Quality of life in noncompliant adults with phenylketonuria after resumption of the diet

Relationship satisfaction in adults with phenylketonuria is positively associated with following recommended treatment, having a partner involved in management, and maintaining good health

RATIONALE

Phenylketonuria (PKU) is a metabolic condition that requires treatment for life. There is increasing evidence that chronic illnesses put strain on relationships and marriages. However, no studies have examined the unique factors that metabolic conditions have on affected individuals and their relationship satisfaction. We surveyed a population of adult patients with PKU and assessed how management, treatment, and lifestyle factors impact their relationship satisfaction.

PURPOSE

The purpose of our study was to explore whether factors such as involvement of partner in PKU management, impact of challenges unique to PKU (e.g., diet, family planning, mood disturbances), and PKU treatment types were associated with the degree of relationship satisfaction.

METHOD

We surveyed adult patients with PKU (n = 82) who were either currently in or had previously been in a long-term relationship. We developed a 78-question survey that included unique questions regarding lifestyle, treatment, and management of their PKU in addition to a validated Relationship Assessment Score. Questions included single choice, multiple choice, and 3 open-ended questions.

RESULTS

We found that higher relationship satisfaction was associated with increased partner involvement, increased health, and adherence to recommended PKU treatments. Participants utilizing both diet and pharmaceutical treatment had the highest relationship satisfaction. Finally, participants who reported that their PKU did not contribute to the ending of a previous relationship reported higher relationship satisfaction scores.

CONCLUSION

This study suggests that involvement of partners in the management and treatment of a chronic illness and adherence to recommended treatments can significantly improve relationship satisfaction.

Adult PKU Clinics in the UK-Users' Experiences and Perspectives

Adults with PKU require life-long management, and ideally, their care should be in a specialised adult metabolic clinic. Their outcomes and co-morbidities have received much attention, but data are lacking on their experience, satisfaction and expectations about the care they receive. This survey reports the experiences and care adults with PKU receive from specialist metabolic clinics in the UK. The online survey developed by the UK NSPKU (National Society for Phenylketonuria), was placed on the NSPKU website from February 2021 to December 2022, and was completed by adults with PKU (≥18 years) or their carers/family members. Sixty-five adult PKU patients and 9 caregivers of adult patients completed the questionnaire (63% female in total). Only 32% of respondents were following a Phe-restricted diet with protein substitute intake as prescribed; the rest were partially adherent or not on dietary restrictions. Nineteen per cent (n = 14/74) had not been reviewed in clinic for two years. Half of the respondents (50%) described their experience in adult clinics as "good". Half of the patients were unable to contact their dietitians with questions or concerns, and only 24% considered that they received adequate support. Clinic reviews usually included anthropometric (82%) and dietary assessments (64%), discussion on management of PKU in daily life (78%) and a blood test (71%). Eighty-eight per cent reported they had at least one neurocognitive, mental health or behavioural co-morbidity but less than half of the patients reported an assessment on their neurocognitive functioning or mental health issues. Adult male patients appeared to have less detailed clinic review than females. Less than half (44%) of the respondents reported that they performed a blood spot for blood Phe at least monthly, but only 32% considered they had been informed about the risk of high Phe levels in adulthood. Although time, cost and stress related to travelling were barriers to a face-to-face review, more than 40% of patients had concerns about remote appointments. The frequency and extent of monitoring of adults with PKU, attending specialist adult services, were less than those specified by the PKU European guidelines. The care of women of reproductive age is prioritised over men. Adult metabolic health services require further attention, development and resources to provide a high standard and equitable service to patients with PKU.

Health-related quality of life in a european sample of adults with early-treated classical PKU

BACKGROUND

Phenylketonuria (PKU) is a rare inborn error of metabolism affecting the catabolism of phenylalanine (Phe). To date, findings regarding health-related quality of life (HRQoL) in adults with early-treated classical PKU are discrepant. Moreover, little is known about metabolic, demographic, and cognitive factors associated with HRQoL. Hence, we aimed to investigate HRQoL and its association with demographic, metabolic, and cognitive characteristics in a large European sample of adults with early-treated classical PKU.

RESULTS

This cross-sectional study included 124 adults with early-treated classical PKU from Hungary, Italy, Spain, Switzerland, and Turkey. All participants prospectively completed the PKU quality of life questionnaire (PKU-QoL), a questionnaire specifically designed to evaluate the impact of PKU and its treatment on HRQoL in individuals with PKU. In addition, information about Phe levels (concurrent and past year), demographic (age and sex), and cognitive variables (intelligence quotient, IQ) were collected. Most domains revealed little or no impact of PKU on HRQoL and more than three-quarters of the patients rated their health status as good, very good, or excellent. Nevertheless, some areas of concern for patients were identified. Patients were worried about the guilt that they experience if they do not adhere to the dietary protein restriction and they were most concerned about high Phe levels during pregnancy. Further, tiredness was the most affected symptom, and the supplements' taste was considered a main issue for individuals with PKU. The overall impact of PKU on HRQoL was higher in women (U = 1315.5, p = .012) and in adults with a lower IQ (rs = - 0.448, p = .005). The overall impact of dietary protein restriction was higher in adults with higher concurrent Phe levels (rs = 0.272, p = .007) and higher Phe levels during the past year (rs = 0.280, p = .009).

CONCLUSION

The impact of PKU on most domains assessed in the PKU-QoL was considered to be low. These results likely reflect the successful implementation of the newborn screening resulting in the prevention of severe adverse long-term outcomes. However, a particular clinical focus should be given to patients with lower IQ, higher Phe levels, and women, as these variables were associated with a lower HRQoL.

Expert Consensus on the Long-Term Effectiveness of Medical Nutrition Therapy and Its Impact on the Outcomes of Adults with Phenylketonuria

Many adults with phenylketonuria (PKU) rely on medical nutrition therapy (MNT; low phenylalanine (Phe) diet with protein substitutes/medical foods) to maintain blood Phe concentrations within recommended ranges and prevent PKU-associated comorbidities. Despite disease detection through newborn screening and introduction of MNT as early as birth, adherence to MNT often deteriorates from childhood onwards, complicating the assessment of its effectiveness in the long term. Via a modified Delphi process, consensus (≥70% agreement) was sought on 19 statements among an international, multidisciplinary 13-member expert panel. After three iterative voting rounds, the panel achieved consensus on 17 statements related to the limitations of the long-term effectiveness of MNT (7), the burden of long-term reliance on MNT (4), and its potential long-term detrimental health effects (6). According to the expert panel, the effectiveness of MNT is limited in the long term, is associated with a high treatment burden, and demonstrates that adults with PKU are often unable to achieve metabolic control through dietary management alone, creating an unmet need in the adult PKU population.

Phenylalanine hydroxylase deficiency treatment and management: A systematic evidence review of the American College of Medical Genetics and Genomics (ACMG)

PURPOSE

Elevated serum phenylalanine (Phe) levels due to biallelic pathogenic variants in phenylalanine hydroxylase (PAH) may cause neurodevelopmental disorders or birth defects from maternal phenylketonuria. New Phe reduction treatments have been approved in the last decade, but uncertainty on the optimal lifespan goal Phe levels for patients with PAH deficiency remains.

METHODS

We searched Medline and Embase for evidence of treatment concerning PAH deficiency up to September 28, 2021. Risk of bias was evaluated based on study design. Random-effects meta-analyses were performed to compare IQ, gestational outcomes, and offspring outcomes based on Phe ≤ 360 μmol/L vs > 360 μmol/L and reported as odds ratio and 95% CI. Remaining results were narratively synthesized.

RESULTS

A total of 350 studies were included. Risk of bias was moderate. Lower Phe was consistently associated with better outcomes. Achieving Phe ≤ 360 μmol/L before conception substantially lowered the risk of negative effect to offspring in pregnant individuals (odds ratio = 0.07, 95% CI = 0.04-0.14; P < .0001). Adverse events due to pharmacologic treatment were common, but medication reduced Phe levels, enabling dietary liberalization.

CONCLUSIONS

Reduction of Phe levels to ≤360 μmol/L through diet or medication represents effective interventions to treat PAH deficiency.

Neuropsychological and quality of life outcomes in PKU patients: expert recommendations of assessment tools in Brazil

BACKGROUND

 Phenylketonuria (PKU) is an inborn error of metabolism caused by deficient activity of phenylalanine hydroxylase. In Brazil, the National Neonatal Screening Program enables early treatment of patients with PKU, which prevents them from developing severe neurological damage and mental disabilities. However, between 20 and 30% of early-treated patients with PKU present focal cognitive deficits, including deficits in working memory, processing speed, and psychiatric symptoms such as anxiety, depression, and attention deficit hyperactivity disorder (ADHD). Therefore, age-specific neuropsychiatric and cognitive tests are important components of PKU patient care. To date, there are no officially approved guidelines or recommendations of tools in Portuguese validated for use in Brazil that could be applied to assess these parameters in patients with PKU.

OBJECTIVE

 To recommend tools validated for use in Brazil that can be used in daily clinical practice to assess quality of life and neuropsychological outcomes in patients with PKU.

METHODS

 Six Brazilian experts discussed about eligible tools based on their clinical experience, the feasibility of their use in clinical routines, and their availability in public health services. Before the meeting, an independent review of the literature was conducted to identify the currently validated tools in Brazil, using the MEDLINE and SciELO databases.

RESULTS

 The experts recommended nine tools to assess quality of life (Peds-QL, SF-36 or WHOQOL-bref), executive function (BRIEF or Bayley-III), IQ (SONR 2½-7[a] or WASI) and ADHD (MTA-SNAP-IV and ASRS).

CONCLUSION

 These instruments may be easily incorporated into clinical practice and improve the quality of multidisciplinary care of patients with PKU.

The impact of metabolic control on cognition, neurophysiology, and well-being in PKU: A systematic review and meta-analysis of the within-participant literature

Phenylketonuria (PKU) is a metabolic disease where Phenylalanine (Phe) rises much above normal levels. Cross-sectional and correlational studies provide valuable information on the importance of maintaining low blood-Phe to achieve good outcomes, but they may be confounded, at least partially, by differences in participant demographics. Moreover, the effect of Phe at older ages is difficult to ascertain because of strong associations between Phe levels across ages. Within-participant studies avoid confounding issues. We have reviewed these studies. We followed PRISMA guidelines to search the literature for studies reporting the impact of Phe changes within participants. Phe was either increased or decreased through diet relaxation/resumption or through pharmacological interventions. Forty-six separate articles reported, singly or in combination, results on cognition (N = 37), well-being (N = 22) and neurophysiological health (N = 14). For all studies, we established, in a binary way, whether a benefit of lower Phe was or was not demonstrated and compared numbers showing benefit versus a null or negative outcome. We then analyzed whether critical parameters (e.g., length of the study/condition for the change, size of Phe change achieved) influenced presence or absence of benefit. For a subset of studies that reported quantitative cognitive outcomes, we carried out a meta-analysis to estimate the size of change in cognitive performance associated with a change in Phe and its significance. There were significantly more studies with benefits than no benefits, both for cognitive and well-being outcomes, and a trend in this direction for neurophysiological outcomes. The meta-analysis showed a highly significant effect size both overall (0.55) and when studies with adults/adolescents were considered separately (0.57). There was some indication that benefits were easier to demonstrate when differences in Phe were larger and achieved across a longer period, but these effects were not always consistent. These results reinforce results from the literature by demonstrating the importance of lower Phe in children as well as in adolescents and adults, even when confounding factors in group composition are eliminated. The field would benefit from further studies where Phe levels are contrasted within-participants to ascertain how much Phe needs to be changed and for how long to see a difference and which measures demonstrate a difference (e.g., which cognitive tasks).

Expert opinion of an Italian working group on the assessment of cognitive, psychological, and neurological outcomes in pediatric, adolescent, and adult patients with phenylketonuria

Phenylketonuria (PKU) is an inherited metabolic disease characterized by a defective conversion of phenylalanine (Phe) to tyrosine, potentially leading to Phe accumulation in the brain. Dietary restriction since birth has led to normal cognitive development. However, PKU patients can still develop cognitive or behavioral abnormalities and subtle neurological deficits. Despite the increasing evidence in the field, the assessment of neurocognitive, psychopathological, and neurological follow-up of PKU patients at different ages is still debated. The high interindividual variability in the cognitive outcome of PKU patients makes the specificity of the neurocognitive and behavioral assessment extremely challenging. In the present paper, a multidisciplinary panel of Italian PKU experts discussed different tools available for cognitive, psychopathological, and neurological assessment at different ages based on the existing literature and daily clinical practice. This study aims to provide evidence and a real-life-based framework for a specific clinical assessment of pediatric, adolescent, and adult patients affected by PKU.

Suitability and Allocation of Protein-Containing Foods According to Protein Tolerance in PKU: A 2022 UK National Consensus

Introduction: There is little practical guidance about suitable food choices for higher natural protein tolerances in patients with phenylketonuria (PKU). This is particularly important to consider with the introduction of adjunct pharmaceutical treatments that may improve protein tolerance. Aim: To develop a set of guidelines for the introduction of higher protein foods into the diets of patients with PKU who tolerate >10 g/day of protein. Methods: In January 2022, a 26-item food group questionnaire, listing a range of foods containing protein from 5 to >20 g/100 g, was sent to all British Inherited Metabolic Disease Group (BIMDG) dietitians (n = 80; 26 Inherited Metabolic Disease [IMD] centres). They were asked to consider within their IMD dietetic team when they would recommend introducing each of the 26 protein-containing food groups into a patient’s diet who tolerated >10 g to 60 g/day of protein. The patient protein tolerance for each food group that received the majority vote from IMD dietetic teams was chosen as its tolerance threshold for introduction. A virtual meeting was held using Delphi methodology in March 2022 to discuss and agree final consensus. Results: Responses were received from dietitians from 22/26 IMD centres (85%) (11 paediatric, 11 adult). For patients tolerating protein ≥15 g/day, the following foods were agreed for inclusion: gluten-free pastas, gluten-free flours, regular bread, cheese spreads, soft cheese, and lentils in brine; for protein tolerance ≥20 g/day: nuts, hard cheeses, regular flours, meat/fish, and plant-based alternative products (containing 5−10 g/100 g protein), regular pasta, seeds, eggs, dried legumes, and yeast extract spreads were added; for protein tolerance ≥30 g/day: meat/fish and plant-based alternative products (containing >10−20 g/100 g protein) were added; and for protein tolerance ≥40 g/day: meat/fish and plant-based alternatives (containing >20 g/100 g protein) were added. Conclusion: This UK consensus by IMD dietitians from 22 UK centres describes for the first time the suitability and allocation of higher protein foods according to individual patient protein tolerance. It provides valuable guidance for health professionals to enable them to standardize practice and give rational advice to patients.

Moving through adulthood: The lived experience of Irish adults with PKU

Background

This paper represents a portion of the findings from one of the first research studies eliciting the lived experience of adults with an early diagnosis of Phenylketonuria (PKU) living in Ireland. Ireland has one of the highest prevalence rates of PKU in Europe, however, little is known about the experience of Irish adults with PKU. Furthermore, Ireland is one of the first countries in the world to introduce neonatal screening followed by the introduction of long-term dietary therapy over 50 years ago. This study presents the first comprehensive assessment of the lived experience of Irish adults with PKU on long term dietary therapy.

Methods

Narrative data was collected from eleven self-selected participants, using semi-structured interviews. The interviews were divided into five sections focused on eliciting a holistic understanding of the lived experience of adults with PKU living in Ireland. Thematic analysis was guided by Colaizzi's Framework (1978) in conjunction with NVivo qualitative data analysis software.

Findings

Findings from the original research encompassed a broad understanding of the lived experience of adults with PKU living in Ireland, including factors influencing dietary therapy and managing PHE blood levels. The themes being discussed within this article are those which appear to be least represented within current literature: living with PKU, including reproductive health, the importance of self-management and establishing routine, support networks in adulthood and concerns regarding aging with PKU.

Conclusion

It was evident from the findings that a diagnosis of PKU can influence how adults with PKU may experience aging and their own mortality. These findings offer new insight into the vulnerability attached to the experience of aging with PKU and may be beneficial to advocacy groups and for future development of policy and practice.

Deubiquitinase USP19 extends the residual enzymatic activity of phenylalanine hydroxylase variants

Phenylalanine hydroxylase (PAH) is a key enzyme in mammals that maintains the phenylalanine (Phe) concentration at an appropriate physiological level. Some genetic mutations in the PAH gene lead to destabilization of the PAH enzyme, leading to phenylketonuria (PKU). Destabilized PAH variants can have a certain amount of residual enzymatic activity that is sufficient for metabolism of Phe. However, accelerated degradation of those variants can lead to insufficient amounts of cellular PAH protein. The optimal protein level of PAH in cells is regulated by a balancing act between E3 ligases and deubiquitinating enzymes (DUBs). In this work, we analyzed the protein expression and stability of two PKU-linked PAH protein variants, R241C and R243Q, prevalent in the Asian population. We found that the tested PAH variants were highly ubiquitinated and thus targeted for rapid protein degradation. We demonstrated that USP19, a DUB that interacts with both PAH variants, plays a regulatory role by extending their half-lives. The deubiquitinating activity of USP19 prevents protein degradation and increases the abundance of both PAH protein variants. Thus, our study reveals a novel mechanism by which deubiquitinating activity of USP19 extends the residual enzymatic activity of PAH variants.

The Impact of the Quality of Nutrition and Lifestyle in the Reproductive Years of Women with PKU on the Long-Term Health of Their Children

A woman’s nutritional status before and during pregnancy can affect the health of her progeny. Phenylketonuria (PKU), a rare disorder causing high blood and brain phenylalanine (Phe) concentrations, is associated with neurocognitive disability. Lifelong treatment is mainly dietetic with a Phe-restricted diet, supplemented with a low-Phe protein substitute. Treatment adherence commonly decreases in adolescence, with some adults ceasing dietary treatment. In maternal PKU, elevated blood Phe is harmful to the fetus so a strict Phe-restricted diet must be re-established preconception, and this is particularly difficult to achieve. A woman’s reproductive years introduces an opportunity to adopt healthier behaviours to prepare for successful pregnancies and positive health outcomes for both themselves and their children. Several factors can influence the health status of women with PKU. Political, socioeconomic, and individual food and lifestyle choices affect diet quality, metabolic control, and epigenetics, which then pre-condition the overall maternal health and long-term health of the child. Here, we reflect on a comprehensive approach to treatment and introduce practical recommendations to optimize the wellbeing of women with PKU and the resultant health of their children.

Measuring Burden of Illness in Phenylketonuria (PKU): Development of the PKU Symptom Severity and Impacts Scale as a Robust Patient-Reported Outcome

Introduction

Phenylketonuria (PKU) is a rare, metabolic genetic disorder that can cause various neuropsychological symptoms that often affect patients’ health-related quality of life, even for patients with good metabolic control. To date, no patient-reported outcomes (PRO) instrument combines the measurement of neuropsychological and dietary concepts to capture the broad impact of PKU on quality of life. This article presents the development of the PKU Symptom Severity and Impacts Scale (PKU-SSIS), a PRO instrument that is designed to evaluate neuropsychological symptoms and impacts in early-treated patients with PKU.

Methods

A draft instrument was developed based on a targeted literature review, PKU expert physician interviews, and an advisory board consisting of patients with PKU. Qualitative interviews combining concept elicitation/cognitive interviews were conducted with patients with classic PKU aged at least 15 years old. A separate sample of 20 patients with PKU completed the draft PKU-SSIS in a paper survey format, to enable preliminary assessment of any floor and ceiling effects.

Results

Patient interviews elicited four key symptom themes: neurocognitive function, emotional and behavioral, physical functioning, and physical health. Four impact themes were also identified: social function, physical health, emotions, and level of independence. No floor or ceiling effects were identified.

Conclusion

The final instrument included 22 items, covering three symptom domains (1. emotional, mood, and psychological; 2. (neuro)cognitive, executive, and intellectual function; and 3. physical health), and four impact domains (1. social relations, 2. level of independence, 3. general well-being, and 4. self-care). The PKU-SSIS will help to address an important gap in the evaluation of existing and future treatments for PKU.

A non-interventional observational study to identify and validate clinical outcome assessments for adults with phenylketonuria for use in clinical trials

Introduction

Current clinical outcome assessments (COAs) are not effectively capturing the complex array of symptoms of adults with phenylketonuria (PKU). This study aimed to identify concepts of interest relevant to adults with PKU. Based on these concepts, COAs for patient-reported outcomes (PROs), observer-reported outcomes (ObsROs), and clinician-reported outcomes (ClinROs) were selected or developed and content validity was assessed.

Materials and methods

Concept-elicitation interviews were conducted with an international cohort of adults with PKU (n = 30), family member observers (n = 14), and clinical experts (n = 8). Observers and clinical experts were included to overcome the risk of lack of self-awareness among adults with PKU. The concepts of interests endorsed by ≥30% of patients, observers, and/or clinical experts were selected, mapped to items in existing COAs, and used to develop global impression items for patients, observers, and clinicians. Next, the content validity of the COAs and global impression items was evaluated by cognitive interviews with patients (n = 22), observers (n = 11), and clinical experts (n = 8). All patients were categorized according to blood phenylalanine (Phe) levels (i.e., <600 μmol/L, 600–1200 μmol/L, and >1200 μmol/L).

Results

Concepts of interests were identified across four domains: emotional, cognitive, physical, and behavioral. After mapping, eight existing COAs were selected based on the concept coverage (six PROs, one ObsRO, and one ClinRO). The six PRO measures were considered as potentially fit-for-purpose. The ObsRO measure was not deemed relevant for use in observers of adults with PKU and only a subscale of the ClinRO measure was considered valid for assessing adults with PKU by clinicians. Due to the lack of existing COAs covering all concepts of interests, global impression items for symptom severity and change in symptoms were developed, which were limited to one question covering in total 14 concepts. Upon validation, some of the patient and observer global impression items were excluded as they were subject to lack of insight or could not be reported by observers. Due to the limited interaction time between clinician and patient, use of the clinician global impression items was not supported.

Conclusion

Existing COAs relevant to adults with PKU were selected and PKU-specific global impression items were developed by mapping the most frequently identified concepts of interests from internationally-conducted in-depth interviews. Future studies should address the appropriateness of the selected COAs and global impression items to assess if these can be used as efficacy endpoints in PKU clinical trials.

Project "Backtoclinic I": An overview on the state of care of adult PKU patients in Austria

BACKGROUND

High rates of lost to follow-up (LTFU) adult patients are a major concern in the long-term management of phenylketonuria (PKU). To address this issue, we designed the project "Backtoclinic" with the purpose of identifying LTFU adult PKU patients in Austria as a first step to reestablish appropriate treatment.

SUBJECTS AND METHODS

Individuals born between 1966 and 1999 and diagnosed with PKU through the National Austrian Newborn Screening Program (NANSP) were identified using the NANSP's database. Follow-up data were collected in the Austrian metabolic centers (Medical University of Vienna, Graz, Innsbruck and Salzburg). Patients with no contact to any of these centers within the previous two years were classified as LTFU. Epidemiological characteristics of the whole study population as well as of LTFU- and currently in follow-up patients were analyzed.

RESULTS

Between 1966 and 1999, 281 individuals were diagnosed with PKU through the NANSP. Two patients died in their first year of life and were excluded from the analysis. Of the remaining 279 patients (mean age ± SD: 36.7 ± 9.1 y, 42.7% females), 177 (63.4%) are currently LTFU. The rate of LTFU patients is higher in men than in women (68.1% vs 57.5%), and markedly increases with age in both sexes. The gender gap is greatest in young adults (52.6% vs. 25.0% in the age range 20.0-24.9 y) and declines with age (94.4% vs. 80.0% in the age range > 45.0 y).

CONCLUSIONS

We found an alarming rate of 63.4% of LTFU adult PKU patients in Austria, and observed a gender gap in the PKU state of care. Our findings illustrate the urgent need for the metabolic community to identify LTFU adult PKU patients and to develop strategies to reestablish appropriate treatment for men and women with PKU.

Newborn screening for inherited metabolic diseases using tandem mass spectrometry in China: Outcome and cost-utility analysis

OBJECTIVES

Few studies in China have focused on the economic evaluation of newborn screening (NBS) for inherited metabolic disorders (IMDs) by tandem mass spectrometry (MS/MS). This study assesses the total costs, benefits, benefit-cost ratio (BCR), cost-utility ratio (CUR) and incremental cost-utility ratio (ICUR) of NBS using MS/MS compared to the non-screened group.

METHODS

The NBS outcomes of newborns who underwent MS/MS screening for IMDs in 2009-2018 were retrospectively reviewed. Records were extracted from a screening management system at the NBS Center of Zhejiang province. A cost-benefit analysis of screening was conducted, assessing screening costs for each subject, and direct and indirect treatment costs for IMDs detected by screening. The putative benefit of clinical outcomes related to early diagnosis was assumed to be improvement in quality of life and prolonged life expectancy in the screened group, as compared to the non-screened group.

RESULTS

Of the 3,040,815 newborns screened, 735 (2.86%) cases were diagnosed through gene sequence analysis. The most frequently occurring types of IMD were amino acid disorders (n = 276), then fatty acid oxidation disorders (n = 248), followed by organic acidaemias (n = 211). The difference in quality-adjusted life-years (QALYs) ranged from 0.78 to 15.4 in the screened group. The CUR was CNY¥ 116,183.89/QALY in the screened group and CNY¥ 3,078,823.65/QALY in the non-screened group. The ICUR was CNY¥ -768,428.76/QALY, and the BCR was 6.09.

CONCLUSIONS

NBS using MS/MS can be considered cost-effective in China. The nationwide promotion of NBS using MS/MS deserves priority consideration and sufficient publicity.

Phenylketonuria

Phenylketonuria (PKU; also known as phenylalanine hydroxylase (PAH) deficiency) is an autosomal recessive disorder of phenylalanine metabolism, in which especially high phenylalanine concentrations cause brain dysfunction. If untreated, this brain dysfunction results in severe intellectual disability, epilepsy and behavioural problems. The prevalence varies worldwide, with an average of about 1:10,000 newborns. Early diagnosis is based on newborn screening, and if treatment is started early and continued, intelligence is within normal limits with, on average, some suboptimal neurocognitive function. Dietary restriction of phenylalanine has been the mainstay of treatment for over 60 years and has been highly successful, although outcomes are still suboptimal and patients can find the treatment difficult to adhere to. Pharmacological treatments are available, such as tetrahydrobiopterin, which is effective in only a minority of patients (usually those with milder PKU), and pegylated phenylalanine ammonia lyase, which requires daily subcutaneous injections and causes adverse immune responses. Given the drawbacks of these approaches, other treatments are in development, such as mRNA and gene therapy. Even though PAH deficiency is the most common defect of amino acid metabolism in humans, brain dysfunction in individuals with PKU is still not well understood and further research is needed to facilitate development of pathophysiology-driven treatments.

Health economic burden of patients with phenylketonuria (PKU) - A retrospective study of German health insurance claims data

This retrospective matched-cohort analysis compared health-economic burdens of adults (≥18 years; n = 377) with phenylketonuria (PKU) and age/gender-matched non-PKU controls (n = 3770) in Germany. Healthcare costs and resource-utilization were analyzed for the year 2015. Differences between groups were tested using 95% CI of mean differences (MD). PKU patients had significantly higher mean costs in total (MD €3307, 95% CI €1736–€4879), for pharmaceuticals (MD €1912, 95% CI €1195–€2629) [including dietary amino-acid supplements (MD €1268, 95% CI €864–€1672)], and outpatient costs (MD €395, 95% CI €115–€675). Inpatient costs (MD €904, 95% CI -€293 to €2100) and costs for aids and remedies (MD €97, 95% CI -€10 to €203) were also higher in PKU patients. PKU patients had more outpatient visits and stayed longer in hospital. Adult PKU patients incur higher total healthcare costs than non-PKU controls, especially regarding pharmaceuticals and outpatient costs, and more frequent resource-utilization, resulting in higher health-economic burden for the statutory healthcare system.

Everyday Life, Dietary Practices, and Health Conditions of Adult PKU Patients: A Multicenter, Cross-Sectional Study

BACKGROUND

Only few data on dietary management of adult phenylketonuria (PKU) patients are published.

OBJECTIVES

This study aimed to assess living situation, dietary practices, and health conditions of early-treated adult PKU patients.

METHODS

A total of 183 early-treated PKU patients ≥18 years from 8 German metabolic centers received access to an online survey, containing 91 questions on sociodemographic data, dietary habits, and health conditions.

RESULTS

144/183 patients (66% females) completed the questionnaire. Compared with German population, the proportion of single-person households was higher (22 vs. 47%), the rate of childbirth was lower (1.34 vs. 0.4%), but educational and professional status did not differ. 82% of the patients adhered to a low-protein diet, 45% consumed modified low-protein food almost daily, and 84% took amino acid mixtures regularly. 48% of the patients never interrupted diet, and 14% stopped diet permanently. 69% of the patients reported to feel better with diet, and 91% considered their quality of life at least as good. The prevalence of depressive symptoms was high (29%) and correlated significantly to phenylalanine blood concentrations (p = 0.046). However, depressive symptoms were only mild in the majority of patients.

CONCLUSION

This group of early-treated adult German PKU patients is socially well integrated, reveals a surprisingly high adherence to diet and amino acid intake, and considers the restrictions of diet to their daily life as low.

[Dietary treatment of inborn errors of metabolism-a balancing act between indulgence and therapy]

For many inborn metabolic diseases, a lifelong diet is a crucial part of the therapy since pharmacological therapy is available for only a few conditions and patients. The implementation of a low natural protein diet with a reduced intake of natural protein and the complementary use of synthetic amino acid mixtures is described using the examples of phenylketonuria and urea cycle disorders focusing on children and adolescents. For phenylketonuria, the amino acid supplement is free of phenylalanine whereas for urea cycle disorders, it exclusively consists of essential amino acids. The dietary treatment aims to maintain metabolic stability and to prevent accumulation of toxic metabolites. At the same time, the nutritional requirements to ensure growth and development must be met. Therefore, patients need to follow strict rules regarding the choice of food products. This restrictive therapy interferes with the desire for autonomy and the joy of eating and often results in a reduced quality of life.Following the diet is crucial for a favorable outcome. To meet its requirements, patients and their families are provided with training. It is a great challenge not only to support the patients and their families in all practical aspects of dietary management, but also to motivate them to lifelong adherence in order to ensure the best possible outcome.

Development of an inventory to assess perceived barriers related to PKU treatment

BACKGROUND

According to studies of phenylketonuria (PKU), the Brazilian population's metabolic control shows unsatisfactory indexes from childhood. Research on patients' perceived difficulties or barriers to adherence to treatment can help us to comprehend how these outcomes are associated. The present study aimed to: (1) describe the development of an inventory for identifying the most frequent and relevant perceived barriers to PKU treatment from the perspective of patients, caregivers, and healthcare professionals; (2) evaluate certain psychometric characteristics of the new measure; and, (3) explore potential predictors (sociodemographic and medical characteristics) that may contribute to increasing the number of perceived barriers and examine whether the number of barriers is associated with the degree of adherence shown by the patient.

RESULTS

Participants in the study were 23 patients with PKU (M age = 18.0 years; SD = 7.3; range 6 to 34 years; 69% early-treated) in classical (n = 11) and mild (n = 12) form, and 11 caregivers. The inventory, developed to ascertain perceived barriers to treatment, was completed by patients (≥ 13 years) and caregivers of patients aged 6 to 17 years. Analyses were conducted to investigate whether barrier inventory scores were associated with adherence to treatment as measured by phenylalanine levels in patients' medical records. Scores on the inventory differed across the patient age groups: adolescents had lower scores (i.e. reported fewer barriers) compared with those of adults (U = 8.000, p = 0.008); patients with better recent metabolic control also reported fewer perceived barriers than did patients with poor adherence (U = 20.000, p = 0.009); and the number of perceived barriers was positively associated with recent blood phenylalanine concentration (Kendall's taub = 0.41; p = 0.001).

CONCLUSIONS

These results suggest that the inventory has merit in assessing perceived barriers and support the need for further research on barriers perceived by PKU patients.

Health Related Quality of Life assessment among early-treated Hungarian adult PKU patients using the PKU-QOL adult questionnaire

Background: The implementation of neonatal screening and the early initiation of lifelong therapy have helped to prevent severe complications and enabled much more favorable outcomes for early-treated phenylketonuria (ETPKU) patients. However, PKU patients tend to develop subtle cognitive and psychosocial abnormalities and the strict dietary therapy can present financial and social burden. Thus, PKU is expected to affect the quality of life (QoL) of these patients. There is insufficient evidence regarding the relationship between metabolic control and Health-Related QoL (HRQoL). We aimed to assess the effect of short- and long-term therapy on QoL among Hungarian adult PKU patients using the standardized PKU-specific PKU-QoL questionnaire.

Methods: We conducted a single-centre, cross-sectional, observational study in Hungary. We included adult PKU patients treated with diet and amino acid supplements only. Patients reported HRQoL using the standardized adult PKU-QoL questionnaire and mean blood Phe concentrations were assessed for three different time periods: the previous 10 years, the previous year and concentration at the time of completing the questionnaire. The correlation between patients’ QoL scores and their Phe levels was assessed. The classical PKU group was further divided into “good” and “suboptimal” adherence groups based on individual mean Phe levels in the examined time period. We evaluated differences in QoL among the two subgroups of classical PKU patients. QoL scores between classical and non-classical patients were also compared.

Results: Data from 88 adult patients were analysed (66 had classical PKU). No median PKU-QoL score reached major or severe impact/frequent symptoms in any domain. The highest scores (meaning larger burden) were mostly related to emotional impact of PKU and disease management. When performing correlation analysis between Phe levels and QoL scores by all patients we found weak to fair positive correlation in several domains either short or long term. Patients with classical PKU reported greater financial impact of PKU than patients with less severe PKU. Classical PKU patients with good therapy adherence tended to report better HRQoL scores than patients with suboptimal adherence.

Conclusion: We conclude that patients showed good HRQoL using the PKU-specific questionnaire. Our study demonstrates that suboptimal metabolic control is negatively associated with patients' HRQoL.

Impact of phenylalanine on cognitive, cerebral, and neurometabolic parameters in adult patients with phenylketonuria (the PICO study): a randomized, placebo-controlled, crossover, noninferiority trial

Background

The population of adult patients with early-treated phenylketonuria (PKU) following newborn screening is growing substantially. The ideal target range of blood phenylalanine (Phe) levels in adults outside pregnancy is a matter of debate. Therefore, prospective intervention studies are needed to evaluate the effects of an elevated Phe concentration on cognition and structural, functional, and neurometabolic parameters of the brain.

Methods

The PICO (Phenylalanine and Its Impact on Cognition) Study evaluates the effect of a 4-week Phe load on cognition and cerebral parameters in adults with early-treated PKU in a double-blind, randomized, placebo-controlled, crossover, noninferiority trial.

Participants

Thirty adult patients with early-treated PKU and 30 healthy controls comparable to patients with regard to age, sex, and educational level will be recruited from the University Hospitals Bern and Zurich, Switzerland. Patients are eligible for the study if they are 18 years of age or older and had PKU diagnosed after a positive newborn screening and were treated with a Phe-restricted diet starting within the first 30 days of life.

Intervention: The cross-over intervention consists of 4-week oral Phe or placebo administration in patients with PKU. The study design mimics a Phe-restricted and a Phe-unrestricted diet using a double-blinded, placebo-controlled approach.

Objectives

The primary objective of the PICO Study is to prospectively assess whether a temporarily elevated Phe level influences cognitive performance (working memory assessed with a n-back task) in adults with early-treated PKU. As a secondary objective, the PICO Study will elucidate the cerebral (fMRI, neural activation during a n-back task; rsfMRI, functional connectivity at rest; DTI, white matter integrity; and ASL, cerebral blood flow) and neurometabolic mechanisms (cerebral Phe level) that accompany changes in Phe concentration. Cognition, and structural and functional parameters of the brain of adult patients with early-treated PKU will be cross-sectionally compared to healthy controls. All assessments will take place at the University Hospital Bern, Switzerland.

Randomization

Central randomization will be used to assign participants to the different treatment arms with age, sex, and center serving as the stratification factors. Randomization lists will be generated by an independent statistician.

Blinding: All trial personnel other than the statistician generating the randomization list and the personnel at the facility preparing the interventional product are blinded to the assigned treatment.

Discussion

Using a combination of neuropsychological and neuroimaging data, the PICO Study will considerably contribute to improve the currently insufficient level of evidence on how adult patients with early-treated PKU should be managed.

Trial registration

The study is registered at clinicaltrials.gov (NCT03788343) on the 27th of December 2018, at kofam.ch (SNCTP000003117) on the 17th of December 2018, and on the International Clinical Trials Registry Platform of the WHO.

Nutritional and Metabolic Characteristics of UK Adult Phenylketonuria Patients with Varying Dietary Adherence

The nutritional and metabolic characteristics of adult phenylketonuria (PKU) patients in the UK with varying dietary adherence is unknown. In other countries, nutritional and metabolic abnormalities have been reported in nonadherent patients compared to adherent counterparts. A pooled analysis of primary baseline data from two UK multi-centre studies was therefore performed to establish whether this is true from a UK perspective. Adult PKU patients who had provided 3-day food records and amino acid blood samples were included and grouped according to dietary adherence (adherent; n = 16 vs. nonadherent; n = 14). Nonadherent patients consumed greater amounts of natural protein compared to adherent patients (61.6 ± 30.7 vs. 18.3 ± 7.7 g/day; q < 0.001). In contrast, the contribution of protein substitutes to total protein intake was lower in nonadherent compared to adherent patients (3.9 ± 9.2 g/day vs. 58.6 ± 10.2 g/day; q < 0.001). Intakes of iron, zinc, vitamin D₃, magnesium, calcium, selenium, iodine, vitamin C, vitamin A and copper were significantly lower in nonadherent compared to adherent patients and were below UK Reference Nutrient Intakes. Similarly, intakes of thiamin, riboflavin, niacin, vitamin B₆ and phosphorus were significantly lower in nonadherent compared to adherent patients but met the UK Reference Nutrient Intakes. Phenylalanine concentrations in nonadherent patients were significantly higher than adherent patients (861 ± 348 vs. 464 ± 196 µmol/L; q=0.040) and fell outside of European treatment target ranges. This study shows the nutritional and metabolic consequences of deviation from phenylalanine restriction and intake of PKU protein substitutes in nonadherent adult PKU patients. Collectively, these data further underlie the importance of life-long adherence to the PKU diet.

A benefit-risk analysis of pegvaliase for the treatment of phenylketonuria: A study of patients' preferences

Background

Phenylketonuria (PKU) leads to an accumulation of phenylalanine (Phe) in the blood and subsequent neurologic, cognitive, psychiatric, and behavioral dysfunction. Many patients report social isolation and decreased quality of life. Pegvaliase is an enzyme substitution therapy that reduces blood Phe levels in patients with PKU and is associated with a risk of hypersensitivity reactions.

Objective

To define the minimum acceptable benefit (MAB) of pegvaliase, i.e., the minimum probability of achieving a blood Phe level <360 μmol/L, which patients require to tolerate the risks of hypersensitivity associated with pegvaliase.

Methods

Adult, pegvaliase-naïve patients with blood Phe levels >600 μmol/L participated in a patient-preference web survey using two surveys: adapted swing-weighting and thresholding. Participants were asked to make ordinal choices between varying clinical benefit and severity levels for hypersensitivity. Disease effects and treatment satisfaction were also assessed.

Results

Among 45 participants, the mean (standard deviation) self-reported blood Phe level was 976.9 (429.9) μmol/L; only 28.8% reported satisfaction with their current treatment. Most (84.4%) indicated difficulty in following a PKU diet; 60% reported that the PKU diet was burdensome, and 58% reported feeling socially isolated. Most (≥69%) reported their MAB to be less than the expected clinical benefit provided by pegvaliase; the mean MAB was 22.7% and 34.4% in the swing-weighting and thresholding surveys, respectively.

Conclusion

Most participants felt the burden of PKU on their daily lives, were dissatisfied with current treatments, and were willing to accept the risks of hypersensitivity reactions to achieve recommended blood Phe levels with pegvaliase treatment.

Pegvaliase: Immunological profile and recommendations for the clinical management of hypersensitivity reactions in patients with phenylketonuria treated with this enzyme substitution therapy

OBJECTIVE

To provide recommendations for managing hypersensitivity adverse events (HAEs) to an injectable enzyme substitution therapy (pegvaliase, a PEGylated phenylalanine ammonia lyase enzyme) in adult patients with phenylketonuria (PKU).

METHODS

Eight European academic immunology experts with a broad range of experience in hypersensitivity, anaphylaxis, and/or drug reactions, and two geneticists from the USA with pegvaliase experience convened for two advisory board meetings. Efficacy, safety, and immunological profile of pegvaliase were discussed with the objective of developing recommendations for the clinical management of HAEs associated with pegvaliase treatment.

RESULTS

Based on available immunogenicity data, it was concluded that pegvaliase induces a Type III hypersensitivity reaction, causing HAEs with peak event rates during induction/titration and a decline over time during maintenance therapy. The decline in HAEs with longer duration of therapy was considered to likely be driven by anti-drug antibody affinity maturation, reduced immune complex formation, and decreased complement activation over time. Immunology and PKU experts unanimously supported that the use of an induction, titration, and maintenance dosing regimen and implementation of several risk mitigation strategies contributed to the improvement of tolerability over time. Key risk mitigation strategies utilized in the Phase 3 clinical trials such as premedication with H1-receptor antagonists, allowance for a longer titration period after an HAE, patient education, and requirement to carry auto-injectable adrenaline (epinephrine) should be continued in clinical practice. A tool for administration of auto-injectable adrenaline in patients using pegvaliase was suggested. It was added that after the occurrence of a severe HAE a temporary dose reduction is more likely to improve tolerability than treatment interruption.

CONCLUSIONS

Overall, it was agreed that pegvaliase has a generally tolerable safety profile in adults with PKU. Importantly, the risk mitigation strategies utilized in the clinical trials were considered to support the continued use of key strategies for management in the commercial setting, such as a slow induction/titration dosing paradigm and premedication with H1-receptor antagonists. However, physicians and patients need to be aware of the risk of HAEs associated with pegvaliase; presence of a trained observer during early treatment may be beneficial in certain circumstances, and a requirement to carry auto-injectable adrenaline is recommended. Because pegvaliase offers the possibility to normalize diet, while maintaining blood phenylalanine within the recommended therapeutic range, safe use of this medication in the clinical setting is important. Ongoing monitoring of long-term clinical safety of patients on pegvaliase treatment in the commercial setting was recommended.

Improved Eating Behaviour and Nutrient Intake in Noncompliant Patients with Phenylketonuria after Reintroducing a Protein Substitute: Observations from a Multicentre Study

Noncompliance is widespread in adults with PKU and is associated with adverse metabolic, nutritional and cognitive abnormalities. Returning to the PKU diet is important for this at-risk population, yet for many this is challenging to achieve. Strategies that ease the return to the PKU diet, while offering nutritional and cognitive advantages, are needed. Twelve PKU adults (33.7 ± 2.6 years), who had been noncompliant for 4.5 years (range: 1 to 11 years), took 33 g of a low-volume, nutrient-enriched, protein substitute daily for 28 days. Outcomes of eating behaviour, nutrient intake and mood were assessed at entry (baseline, days 1-3) and after the intervention period (days 29-31). At baseline, intakes of natural protein and estimated phenylalanine were high (66.4 g and 3318.5 mg, respectively) and intakes of calcium, magnesium, iron, zinc, iodine and vitamin D were below country-specific recommendations. With use of the experimental protein substitute, natural protein and estimated phenylalanine intake declined (p = 0.043 for both). Fat and saturated fat intakes also decreased (p = 0.019 and p = 0.041, respectively), while energy and carbohydrate intake remained unchanged. Micronutrient intake increased (p ≤ 0.05 for all aforementioned) to levels well within reference nutrient intake recommendations. Blood vitamin B₁₂ and vitamin D increased by 19.8% and 10.4%, respectively. Reductions in anxiety and confusion were also observed during the course of the study yet should be handled as preliminary data. This study demonstrates that reintroducing a low-volume, nutrient-enriched protein substitute delivers favourable nutritional and possible mood benefits in noncompliant PKU patients, yet longer-term studies are needed to further confirm this. This preliminary knowledge should be used in the design of new strategies to better facilitate patients' return to the PKU diet, with the approach described here as a foundation.

Clinical burden of illness in patients with phenylketonuria (PKU) and associated comorbidities - a retrospective study of German health insurance claims data

BACKGROUND

Phenylketonuria (PKU) is an inherited deficiency in the enzyme phenylalanine hydroxylase (PAH), which, when poorly-managed, is associated with clinical features including deficient growth, microcephaly, seizures, and intellectual impairment. The management of PKU should start as soon as possible after diagnosis to prevent irreversible damage and be maintained throughout life. The aim of this study was to assess the burden of illness in PKU patients in general and in PKU patients born before and after the introduction of newborn screening in Germany.

METHODS

This retrospective matched cohort analysis used the Institut für angewandte Gesundheitsforschung Berlin (InGef) research database containing anonymized healthcare claims of approximately 4 million covered lives. PKU patients were compared with matched controls from the general population within the same database (1:10 ratio via direct, exact matching on age and gender without replacement). PKU patients were included if they were aged ≥18 years on 01/01/15 and were continuously enrolled from 01/01/10 to 31/12/15. The 50 most commonly reported comorbidities and 50 most commonly prescribed medications in the PKU population were analyzed. Differences between groups were tested using 95% confidence interval (CI) of prevalence ratio (PR) values.

RESULTS

The analysis included 377 adult PKU patients (< 5 of which were receiving sapropterin dihydrochloride) and 3,770 matched controls. Of the 50 most common comorbidities in the PKU population, those with a statistically significant PR > 1.5 vs controls included major depressive disorders (PR = 2.3), chronic ischemic heart disease (PR = 1.7), asthma (PR = 1.7), dizziness and giddiness (PR = 1.8), unspecified diabetes mellitus (PR = 1.7), infectious gastroenteritis and colitis (PR = 1.7), and reaction to severe stress and adjustment disorders (PR = 1.6). The most commonly prescribed Anatomical Therapeutic Chemical (ATC) subcodes among PKU patients (vs the control population) are for systemic antibacterials (34.7% vs 32.8%), anti-inflammatory and antirheumatic (29.4% vs 27.5%), renin-angiotensin agents (30.0% vs 27.0%), acid-related disorders (29.4% vs 20.2%), and beta-blockers (24.9% vs 19.9%).

CONCLUSION

The overall clinical burden on patients with PKU is exacerbated by a significantly higher risk of numerous comorbidities and hence, prescribing of the requisite medication, both for recognized (e.g. major depressive disorders) and more unexpected comorbidities (e.g. ischemic heart disease).

The neurological and psychological phenotype of adult patients with early-treated phenylketonuria: A systematic review

Newborn screening for phenylketonuria (PKU) and early introduction of dietary therapy has been remarkably successful in preventing the severe neurological features of PKU, including mental retardation and epilepsy. However, concerns remain that long-term outcome is still suboptimal, particularly in adult patients who are no longer on strict phenylalanine-restricted diets. With our systematic literature review we aimed to describe the neurological phenotype of adults with early-treated phenylketonuria (ETPKU). The literature search covered the period from 1 January 1990 up to 16 April 2018, using the NLM MEDLINE controlled vocabulary. Of the 643 records initially identified, 83 were included in the analysis. The most commonly reported neurological signs were tremor and hyperreflexia. The overall quality of life (QoL) of ETPKU adults was good or comparable to control populations, and there was no evidence for a significant incidence of psychiatric disease or social difficulties. Neuroimaging revealed that brain abnormalities are present in ETPKU adults, but their clinical significance remains unclear. Generally, intelligence quotient (IQ) appears normal but specific deficits in neuropsychological and social functioning were reported in early-treated adults compared with healthy individuals. However, accurately defining the prevalence of these deficits is complicated by the lack of standardized neuropsychological tests. Future research should employ standardized neurological, neuropsychological, and neuroimaging protocols, and consider other techniques such as advanced imaging analyses and the recently validated PKU-specific QoL questionnaire, to precisely define the nature of the impairments within the adult ETPKU population and how these relate to metabolic control throughout life.

Evidence- and consensus-based recommendations for the use of pegvaliase in adults with phenylketonuria

Purpose

Phenylketonuria (PKU) is a rare metabolic disorder that requires life-long management to reduce phenylalanine (Phe) concentrations within the recommended range. The availability of pegvaliase (PALYNZIQ™, an enzyme that can metabolize Phe) as a new therapy necessitates the provision of guidance for its use.

Methods

A Steering Committee comprising 17 health-care professionals with experience in using pegvaliase through the clinical development program drafted guidance statements during a series of face-to-face meetings. A modified Delphi methodology was used to demonstrate consensus among a wider group of health-care professionals with experience in using pegvaliase.

Results

Guidance statements were developed for four categories: (1) treatment goals and considerations prior to initiating therapy, (2) dosing considerations, (3) considerations for dietary management, and (4) best approaches to optimize medical management. A total of 34 guidance statements were included in the modified Delphi voting and consensus was reached on all after two rounds of voting.

Conclusion

Here we describe evidence- and consensus-based recommendations for the use of pegvaliase in adults with PKU. The manuscript was evaluated against the Appraisal of Guidelines for Research and Evaluation (AGREE II) instrument and is intended for use by health-care professionals who will prescribe pegvaliase and those who will treat patients receiving pegvaliase.

Patient and observer reported outcome measures to evaluate health-related quality of life in inherited metabolic diseases: a scoping review

Background

Health-related Quality of Life (HrQoL) is a multidimensional measure, which has gained clinical and social relevance. Implementation of a patient-centred approach to both clinical research and care settings, has increased the recognition of patient and/or observer reported outcome measures (PROMs or ObsROMs) as informative and reliable tools for HrQoL assessment. Inherited Metabolic Diseases (IMDs) are a group of heterogeneous conditions with phenotypes ranging from mild to severe and mostly lacking effective therapies. Consequently, HrQoL evaluation is particularly relevant.

Objectives

We aimed to: (1) identify patient and/or caregiver-reported HrQoL instruments used among IMDs; (2) identify the main results of the application of each HrQoL tool and (3) evaluate the main limitations of HrQoL instruments and study design/methodology in IMDs.

Methods

A scoping review was conducted using methods outlined by Arksey and O’Malley. Additionally, we critically analysed each article to identify the HrQoL study drawbacks.

Results

Of the 1954 studies identified, 131 addressed HrQoL of IMDs patients using PROMs and/or ObsROMs, both in observational or interventional studies. In total, we identified 32 HrQoL instruments destined to self- or proxy-completion; only 2% were disease-specific. Multiple tools (both generic and disease-specific) proved to be responsive to changes in HrQoL; the SF-36 and PedsQL questionnaires were the most frequently used in the adult and pediatric populations, respectively. Furthermore, proxy data often demonstrated to be a reliable approach complementing self-reported HrQoL scores. Nevertheless, numerous limitations were identified especially due to the rarity of these conditions.

Conclusions

HrQoL is still not frequently assessed in IMDs. However, our results show successful examples of the use of patient-reported HrQoL instruments in this field. The importance of HrQoL measurement for clinical research and therapy development, incites to further research in HrQoL PROMs’ and ObsROMs’ creation and validation in IMDs.

Electronic supplementary material

The online version of this article (10.1186/s13023-018-0953-9) contains supplementary material, which is available to authorized users.

Reproductive experience of women living with phenylketonuria

Introduction

Many women with PKU are well-informed about the risks of maternal PKU but there are several barriers to achieving satisfactory metabolic control before and during pregnancy. Many studies have documented the outcome of maternal PKU infants, but very little has been reported about the experiences of women of reproductive age with PKU, particularly about their psychosexual development, pre-conception, pregnancy and postnatal experience.

Methods

In the UK, in a subsection of an online questionnaire conducted by the National Society for PKU (NSPKU) about living with PKU, women aged 18 years and over completed 9 closed questions about their pre-conception, pregnancy and post-natal experiences and an open-ended question on their reproductive health.

Results

300 women aged 18 years and over with PKU completed this questionnaire with 37% (n = 111/300) of women already having children. 56% (n = 71/128) of pregnancies were planned and a further 18% (n = 23/128) of women had both planned and unplanned pregnancies. Most women (73%, n = 200/273) expressed concerns, fears and distress about pregnancy and two thirds of women who had at least one pregnancy stated that having PKU made pregnancy more stressful and difficult. 60% (n = 164/273) were concerned that they may cause harm to a baby, 58% (n = 159/273) worried about their ability to manage a strict diet during pregnancy, 54% (n = 147/273) had anxiety about their ability to maintain blood Phe within target range, and 48% (n = 132/273) feared having an unplanned pregnancy.

Postnatally, 48% (n = 45/93) had low mood or sadness, 41% (n = 38/93) were depressed, 34% (n = 32/93) felt unable to cope, 33% (n = 31/93) said they could not manage their PKU and care for their baby, 14% (n = 13/93) struggled with child care needs and 4% (n = 4/94) worried they might hurt themselves or their baby through being unable to manage their diet.

Conclusions

Many women with PKU have unmet sexual and reproductive health needs. Pregnancy fears are prominent from adolescence onwards and for some women overarching concerns about their ability to cope with pregnancy led to a decision not to have children. Interventions are needed to reduce the psychological impact of the risk of maternal PKU syndrome and assist with safe pregnancies. Post-natal experiences of women with PKU give rise to concern.

Association of immune response with efficacy and safety outcomes in adults with phenylketonuria administered pegvaliase in phase 3 clinical trials

BACKGROUND

This study assessed the immunogenicity of pegvaliase (recombinant Anabaena variabilis phenylalanine [Phe] ammonia lyase [PAL] conjugated with polyethylene glycol [PEG]) treatment in adults with phenylketonuria (PKU) and its impact on safety and efficacy.

METHODS

Immunogenicity was assessed during induction, upward titration, and maintenance dosing regimens in adults with PKU (n = 261). Total antidrug antibodies (ADA), neutralizing antibodies, immunoglobulin (Ig) M and IgG antibodies against PAL and PEG, IgG and IgM circulating immune complex (CIC) levels, complement components 3 and 4 (C3/C4), plasma Phe, and safety were assessed at baseline and throughout the study. Pegvaliase-specific IgE levels were measured in patients after hypersensitivity adverse events (HAE).

FINDINGS

All patients developed ADA against PAL, peaking by 6 months and then stabilizing. Most developed transient antibody responses against PEG, peaking by 3 months, then returning to baseline by 9 months. Binding of ADA to pegvaliase led to CIC formation and complement activation, which were highest during early treatment. Blood Phe decreased over time as CIC levels and complement activation declined and pegvaliase dosage increased. HAEs were most frequent during early treatment and declined over time. No patient with acute systemic hypersensitivity events tested positive for pegvaliase-specific IgE near the time of the event. Laboratory evidence was consistent with immune complex-mediated type III hypersensitivity. No evidence of pegvaliase-associated IC-mediated end organ damage was noted.

INTERPRETATION

Despite a universal ADA response post-pegvaliase administration, adult patients with PKU achieved substantial and sustained blood Phe reductions with a manageable safety profile. FUND: BioMarin Pharmaceutical Inc.

Living with Phenylketonuria: Lessons from the PKU community

Introduction

We report the practical, social and psychological issues of living with phenylketonuria (PKU) from one of the largest surveys that has been completed by both adults with PKU and parents/caregivers of children.

Methods

In the UK, parents/caregivers of children and adults with PKU were invited to complete an online survey between November 2017 to January 2018 by the NSPKU (National Society for Phenylketonuria).

Results

631 participants (adults, n = 338; parents/caregivers of children, n = 293) with PKU completed the questionnaire. Problems experienced by children with PKU were: difficulty with maintaining focus (48%, n = 114/236), educational difficulties (28%, n = 67/236), anxiety or depression (29%, n = 68/236), and gastrointestinal symptoms (34%, n = 97/282). Fifty one per cent (n = 120/236) described social exclusion; 17% (n = 41/236) had relationship issues with friends or family. Problems experienced by adults were: depression or anxiety (52%, n = 148/286), difficulty maintaining focus (54%, n = 154/286), and low mood (54%, n = 180/334). Difficulties were experienced with relationships (34%, n = 96/286); social exclusion (44%, n = 126/286); and gastrointestinal issues (n = 34%, n = 112/334). Common medications used included antidepressants (40%, n = 131/331) and anxiolytics (18%, n = 60/334).

Discussions

Adults with PKU or caregivers/parents of children identified significant neurocognitive, mental health and general health issues. Limits on socialisation, perception of social isolation and dietary stigma are major obstacles which are difficult to overcome with conventional dietary management.

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631 participants with PKU or caregivers completed a questionnaire

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Limits on socialisation, perception of social isolation and dietary stigma were major obstacles with conventional dietary management in PKU

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Only one in four patients with PKU received psychological support

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Ambivalent messages from health professionals about the need to follow life-long treatment affected adult commitment to adhere to treatment

The impact of metabolic control and tetrahydrobiopterin treatment on health related quality of life of patients with early-treated phenylketonuria: A PKU-COBESO study

The aim of this study was to examine Health-Related Quality of Life (HRQoL) of patients with Phenylketonuria (PKU) in three different age groups and to investigate the impact of metabolic control and tetrahydrobiopterin (BH4) treatment on HRQoL of these patients. Participants were 90 early-treated patients aged 7 to 40 years (M = 21.0, SD = 10.1) and 109 controls aged 7 to 40.8 years (M = 19.4, SD = 8.6). HRQoL was assessed with the (generic) TNO-AZL questionnaires. Overall, good HRQoL was reported for children below 12 years of age, although they were judged to be less autonomic than their healthy counterparts. Adolescents aged 12-15 years showed poorer HRQoL in the domain "cognitive functioning" compared to controls. For adults ≥16 years, poorer age-controlled HRQoL was found for the domains cognition, depressive moods, and anger, with a further trend for the domain "pain". With respect to metabolic control, only for adult PKU-patients robust associations were observed, indicating poorer functioning, most notably in the domains cognition, sleep, pain, sexuality and anger, with higher historical and concurrent Phe-levels. With respect to BH4-use, effects on HRQoL were again only observed for adult PKU-patients. After controlling for age and historical Phe-levels, small but significant differences in favor of adult BH4-users compared to non-users were observed for HRQoL-categories happiness, anger, and social functioning. Together, these results show that, particularly for adult PKU-patients, HRQoL-problems are evident and that many of these problems are related to (history of) metabolic control. Beneficial effects of BH4-use appear to be limited to those associated with relief from the practical burdens related to the strict dietary treatment regimen, i.e. general mood and sociability, whereas metabolic control is more strongly related to basic physical and cognitive functioning.

Pegvaliase for the treatment of phenylketonuria: A pivotal, double-blind randomized discontinuation Phase 3 clinical trial

INTRODUCTION

Pegvaliase is a recombinant Anabaena variabilis phenylalanine ammonia lyase (PAL) enzyme under investigation for treatment of adult phenylketonuria (PKU). This manuscript describes results of a randomized discontinuation trial (RDT) designed to evaluate the effects of pegvaliase treatment on blood phenylalanine (Phe) and neuropsychiatric outcomes in adults with PKU.

METHODS

PRISM-2 is a 4-part, Phase 3 study that enrolled adults with PKU receiving pegvaliase treatment (initiated in a prior Phase 2 or Phase 3 study). The RDT, Part 2 of PRISM-2, was an 8-week trial that evaluated change in blood Phe concentrations, neuropsychiatric and neurocognitive measures, and safety outcomes in PRISM-2 participants who had achieved at least a 20% blood Phe reduction from pre-treatment baseline with pegvaliase treatment. Participants were randomized 2:1 to either continue pegvaliase (20 mg/day or 40 mg/day) or switch to matching placebo.

RESULTS

The pooled pegvaliase group enrolled 66 participants and each placebo group enrolled 14 participants. The primary endpoint of change in blood Phe concentration from RDT entry to RDT Week 8 was met with clinically meaningful and statistically significant differences between the pegvaliase and placebo groups. Mean (SD) blood Phe at the beginning of the RDT when all participants were receiving pegvaliase was 563.9 μM (504.6) in the group assigned to the 20 mg/day placebo group (n = 14), 508.2 μM (363.7) in those assigned to the 40 mg/day placebo group (n = 14), and 503.9 μM (520.3) in those assigned to continue pegvaliase treatment (n = 58). At Week 8 of the RDT, the least squares mean change (95% confidence interval) in blood Phe was 949.8 μM (760.4 to 1139.1) for the 20 mg/day placebo group and 664.8 μM (465.5 to 864.1) for the 40 mg/day placebo group in comparison to 26.5 μM (-68.3 to 121.3) for the pooled (20 mg/day and 40 mg/day) pegvaliase group (P < 0.0001 for pooled pegvaliase group vs each placebo group). Adverse events (AEs) were usually lower in the pooled placebo group when compared to the pooled pegvaliase group. The most common AEs for the pooled pegvaliase and pooled placebo groups were arthralgia (13.6% and 10.3%, respectively), headache (12.1% and 24.1%), anxiety (10.6% and 6.9%), fatigue (10.6% and 10.3%), and upper respiratory tract infection (1.5% and 17.2%).

CONCLUSION

Mean blood Phe reduction was sustained in the pegvaliase group, while placebo groups had mean blood Phe concentration increase toward pre-treatment baseline levels. Results from this study confirmed the efficacy of pegvaliase in maintaining reduced blood Phe concentrations with a manageable safety profile for most participants.

Pegvaliase for the treatment of phenylketonuria: Results of a long-term phase 3 clinical trial program (PRISM)

BACKGROUND

Phenylketonuria (PKU) is caused by phenylalanine hydroxylase (PAH) deficiency that results in phenylalanine (Phe) accumulation. Pegvaliase, PEGylated recombinant Anabaena variabilis phenylalanine ammonia lyase (PAL), converts Phe to trans-cinnamic acid and ammonia, and is a potential enzyme substitution therapy to lower blood Phe in adults with PKU.

METHODS

Two Phase 3 studies, PRISM-1 and PRISM-2, evaluated the efficacy and safety of pegvaliase treatment using an induction, titration, and maintenance dosing regimen in adults with PKU. In PRISM-1, pegvaliase-naïve participants with blood Phe >600 μmol/L were randomized 1:1 to a maintenance dose of 20 mg/day or 40 mg/day of pegvaliase. Participants in PRISM-1 continued pegvaliase treatment in PRISM-2, a 4-part clinical trial that includes an ongoing, open-label, long-term extension study of pegvaliase doses of 5 mg/day to 60 mg/day.

RESULTS

Of 261 participants who received pegvaliase treatment, 72.0% and 32.6% reached ≥12 months and ≥ 24 months of study treatment, respectively, and 65% are still actively receiving treatment. Mean (SD) blood Phe was 1232.7 (386.4) μmol/L at baseline, 564.5 (531.2) μmol/L at 12 months, and 311.4 (427) μmol/L at 24 months, a decrease from baseline of 51.1% and 68.7%, respectively. Within 24 months, 68.4% of participants achieved blood Phe ≤600 μmol/L, 60.7% of participants achieved blood Phe ≤360 μmol/L, below the upper limit recommended in the American College of Medical Genetics and Genomics PKU management guidelines, and 51.2% achieved blood Phe ≤120 μmol/L, below the upper limit of normal in the unaffected population. Improvements in neuropsychiatric outcomes were associated with reductions in blood Phe and were sustained with long-term pegvaliase treatment. Adverse events (AEs) were more frequent in the first 6 months of exposure (early treatment phase) than after 6 months of exposure (late treatment phase); 99% of AEs were mild or moderate in severity and 96% resolved without dose interruption or reduction. The most common AEs were arthralgia (70.5%), injection-site reaction (62.1%), injection-site erythema (47.9%), and headache (47.1%). Acute systemic hypersensitivity events consistent with clinical National Institute of Allergy and Infectious Diseases and the Food Allergy and Anaphylaxis Network anaphylaxis criteria were observed in 12 participants (17 events); of these, 6 participants remained on treatment. Acute systemic hypersensitivity events including potential events of anaphylaxis were not associated with immunoglobulin E, and all events resolved without sequelae.

CONCLUSION

Results from the PRISM Phase 3 program support the efficacy of pegvaliase for the treatment of adults with PKU, with a manageable safety profile in most participants. The PRISM-2 extension study will continue to assess the long-term effects of pegvaliase treatment.

Blood phenylalanine instability strongly correlates with anxiety in phenylketonuria

We assessed the relationship between anxiety and long-term metabolic control in adolescents with phenylketonuria (PKU). We used a standardized psychological test to measure anxiety level and analyzed lifelong blood phenylalanine stability in a selected group of 25 PKU teenagers with treatment adherence problems. We demonstrated significant correlations of anxiety with variability of blood phenylalanine concentrations and with severity of hyperphenylalaninemia. Avoiding blood phenylalanine fluctuations in childhood can probably reduce anxiety in PKU adolescents.

Quality of life and adherence to treatment in early-treated Brazilian phenylketonuria pediatric patients

Early dietary treatment of phenylketonuria (PKU), an inborn error of phenylalanine (Phe) metabolism, results in normal cognitive development. Although health-related quality of life (HRQoL) of PKU patients has been reported as unaffected in high-income countries, there are scarce data concerning HRQoL and adherence to treatment of PKU children and adolescents from Brazil. The present study compared HRQoL scores in core dimensions of Brazilian early-treated PKU pediatric patients with those of a reference population, and explored possible relationships between adherence to treatment and HRQoL. Early-treated PKU pediatric patient HRQoL was evaluated by self- and parent-proxy reports of the Pediatric Quality of Life Inventory (PedsQL) core scales. Adherence to treatment was evaluated by median Phe levels and percentage of results within the therapeutic target range in two periods. Means for total and core scales scores of PedsQL self- and parent proxy-reports of PKU patients were significantly lower than their respective means for controls. Adequacy of median Phe concentrations and the mean percentage of values in the target range fell substantially from the first year of life to the last year of this study. There was no significant difference in mean total and core scale scores for self- and parent proxy-reports between patients with adequate and those with inadequate median Phe concentrations. The harmful consequences for intellectual capacity caused by poor adherence to dietary treatment could explain the observed decrease in all HRQoL scales, especially in school functioning. Healthcare system and financial difficulties may also have influenced negatively all HRQoL dimensions.

Large neutral amino acid supplementation as an alternative to the phenylalanine-restricted diet in adults with phenylketonuria: evidence from adult Pah-enu2 mice

Phenylketonuria treatment mainly consists of a phenylalanine-restricted diet but still results in suboptimal neuropsychological outcome, which is at least partly based on cerebral monoamine deficiencies, while, after childhood, treatment compliance decreases. Supplementation of large neutral amino acids (LNAAs) was previously demonstrated in young phenylketonuria mice to target all three biochemical disturbances underlying brain dysfunction in phenylketonuria. However, both its potential in adult phenylketonuria and the comparison with the phenylalanine-restricted diet remain to be established. To this purpose, several LNAA supplements were compared with a severe phenylalanine-restricted diet with respect to brain monoamine and amino acid concentrations in adult C57Bl/6 Pah-enu2 mice. Adult phenylketonuria mice received a phenylalanine-restricted diet, unrestricted diet supplemented with several combinations of LNAAs or AIN-93M control diet for 6 weeks. In addition, adult wild-type mice on AIN-93M diet served as controls. The severe phenylalanine-restricted diet in adult phenylketonuria mice significantly reduced plasma and brain phenylalanine and restored brain monoamine concentrations, while brain concentrations of most nonphenylalanine LNAAs remained subnormal. Supplementation of eight LNAAs was similarly effective as the severe phenylalanine-restricted diet to restore brain monoamines, while brain and plasma phenylalanine concentrations remained markedly elevated. These results provide biochemical support for the effectiveness of the severe phenylalanine-restricted diet and showed the possibilities of LNAA supplementation being equally effective to restore brain monoamines in adult phenylketonuria mice. Therefore, LNAA supplementation is a promising alternative treatment to phenylalanine restriction in adult phenylketonuria patients to further optimize neuropsychological functioning.

The complete European guidelines on phenylketonuria: diagnosis and treatment

Phenylketonuria (PKU) is an autosomal recessive inborn error of phenylalanine metabolism caused by deficiency in the enzyme phenylalanine hydroxylase that converts phenylalanine into tyrosine. If left untreated, PKU results in increased phenylalanine concentrations in blood and brain, which cause severe intellectual disability, epilepsy and behavioural problems. PKU management differs widely across Europe and therefore these guidelines have been developed aiming to optimize and standardize PKU care. Professionals from 10 different European countries developed the guidelines according to the AGREE (Appraisal of Guidelines for Research and Evaluation) method. Literature search, critical appraisal and evidence grading were conducted according to the SIGN (Scottish Intercollegiate Guidelines Network) method. The Delphi-method was used when there was no or little evidence available. External consultants reviewed the guidelines. Using these methods 70 statements were formulated based on the highest quality evidence available. The level of evidence of most recommendations is C or D. Although study designs and patient numbers are sub-optimal, many statements are convincing, important and relevant. In addition, knowledge gaps are identified which require further research in order to direct better care for the future.

Key European guidelines for the diagnosis and management of patients with phenylketonuria

We developed European guidelines to optimise phenylketonuria (PKU) care. To develop the guidelines, we did a literature search, critical appraisal, and evidence grading according to the Scottish Intercollegiate Guidelines Network method. We used the Delphi method when little or no evidence was available. From the 70 recommendations formulated, in this Review we describe ten that we deem as having the highest priority. Diet is the cornerstone of treatment, although some patients can benefit from tetrahydrobiopterin (BH4). Untreated blood phenylalanine concentrations determine management of people with PKU. No intervention is required if the blood phenylalanine concentration is less than 360 μmol/L. Treatment is recommended up to the age of 12 years if the phenylalanine blood concentration is between 360 μmol/L and 600 μmol/L, and lifelong treatment is recommended if the concentration is more than 600 μmol/L. For women trying to conceive and during pregnancy (maternal PKU), untreated phenylalanine blood concentrations of more than 360 μmol/L need to be reduced. Treatment target concentrations are as follows: 120-360 μmol/L for individuals aged 0-12 years and for maternal PKU, and 120-600 μmol/L for non-pregnant individuals older than 12 years. Minimum requirements for the management and follow-up of patients with PKU are scheduled according to age, adherence to treatment, and clinical status. Nutritional, clinical, and biochemical follow-up is necessary for all patients, regardless of therapy.

Phenylketonuria patients' and their parents' knowledge and attitudes to the daily diet - multi-centre study

Background

The aim of the study was to assess both patients’ and their parents’ knowledge of phenylketonuria (PKU) treatment and compliance with PKU diet.

Methods

The study included 173 PKU patients aged 10–19 and 110 parents of PKU children who were enrolled in the study on the basis of questionnaire data. The study also included 45 patients aged ≥20.

Results

Our study demonstrated that only 45% (n = 74) of PKU patients knew daily Phe intake recommendations, 27% of patients (n = 41) knew the Phe content in a minimum of three out of four researched food products. Patients’ knowledge concerning Phe intake (p = 0.0181) and the knowledge of selected food products (p = 0.041819) improved with age. We did not establish such a correlation in the group of PKU children’s parents.

Approximately 31% of patients and 22% of parents reported helplessness, which increased with the child’s age, associated with the necessity to adhere to the diet; 30% of patients reported feeling ashamed of the fact that they could not eat all food products. Regardless of age, children were more likely than parents to report helplessness (p = 0.032005).

Among patients, 41.40% declared that they would wish to select products unassisted but their parents did not permit them to do so. The question of whether parents teach children self-reliance in meal preparation was answered affirmatively by 98% of parents and only 81% of children (p = 0.0001).

Conclusion

Our data demonstrated that parents’ and children’s knowledge concerning treatment recommendations and food products does not have a direct impact on attitude to the PKU diet. Limiting children’s independence in meal selection, growing helplessness in the face of dietary adherence and shame resulting from the necessity to follow a different diet observed in PKU families are responsible for shaping and perpetuating a consistently negative attitude to the diet. The care of PKU paediatric patients requires consistent, long-term family and individual therapy which may counteract the effects of learned helplessness. In regard to the educational effort, a good parent-child relationship as well as the teaching of behaviours motivating patients to comply with the diet are of great importance.

Electronic supplementary material

The online version of this article (doi:10.1186/s12986-017-0207-1) contains supplementary material, which is available to authorized users.

Dietary patterns, cost and compliance with low-protein diet of phenylketonuria and other inherited metabolic diseases

BACKGROUND/OBJECTIVES

Phenylketonuria (PKU) and several other inherited metabolic diseases (IMD) require a lifelong low-protein diet (LPD), otherwise they lead to many health complications. LPDs, however, carry a significant economic burden for patients and their families. The objective of this study was to explore the costs of low-protein foods (LPFs) necessary for LPD as well as dietary patterns and compliance towards an LPD.

SUBJECTS/METHODS

A detailed questionnaire was created in cooperation with National Association of PKU and other IMD (NSPKU), and consequently sent to all NSPKU members treated with an LPD (n=303). A total of 184 respondents from the Czech Republic were included in the study (174 had PKU, 10 had other IMD).

RESULTS

The average daily consumption of LPF was equal to 411.7 g (PKU) and 345.6 g (other IMD), which corresponds to energy value of 5558 kJ and 4438 kJ, respectively, per patient per day. Patients mostly consumed low-protein flour (≈30% of energy intake), pasta (≈18%), basic pastry (≈15%) and sweets (≈10%). The average monthly costs of LPDs were equal to [euro ]130 (PKU) and [euro ]129 (other IMD) per patient per month. The compliance with LPD was decreasing with increasing age (P<0.0001).

CONCLUSIONS

This is the largest study examining costs and dietary patterns of LPDs in patients with PKU and the first study of this kind in other IMD patients requiring an LPD. The study clearly showed that an LPD carries a very high economic burden for families, which may lead to less LPD compliance and potential severe health consequences.

Development of the US English version of the phenylketonuria - quality of life (PKU-QOL) questionnaire

Background

Phenylketonuria (PKU) is a rare genetic disorder caused by a defect in the metabolism of phenylalanine (PHE) resulting in elevated blood and brain PHE levels, and leading to cognitive, emotional, and psychosocial problems. The phenylketonuria – quality of life (PKU-QOL) questionnaire was the first self-administered disease-specific instrument developed to assess the impact of PKU and its treatment on the health-related quality of life (HRQL) of patients and their caregivers. Available in four versions (child, adolescent, adult and parent), the PKU-QOL was simultaneously developed and validated in seven countries [i.e., France, Germany, Italy, The Netherlands, Spain, Turkey and the United Kingdom (UK)]. The objectives of our study were to develop and linguistically validate the PKU-QOL questionnaire for use in the United States (US).

Methods

The UK versions served as a basis for the development of the US English PKU-QOL questionnaire. The linguistic validation process consisted of 4 steps: 1) adaptation of the UK versions into US English by a translator native of US English and living in the US; 2) a clinician review; 3) cognitive interviews with patients and caregivers to test the appropriateness, understandability and clarity of the US translations; and 4) two proof-readings.

Results

The adaptation from UK to US English revealed the usual syntactic and idiomatic differences between the two languages, such as differences in: 1) Spelling, e.g., “dietician” (UK) vs. “dietitian” (US), or “mum” (UK) vs. “mom” (US); 2) Syntax or punctuation; and 3) Words/expressions use, e.g., “holidays” (UK) vs. “vacation” (US), or “biscuits” (UK) vs. “crackers” (US). The major issue was cultural, and consisted of using a different terminology to describe PKU treatment throughout the questionnaires. The clinician, with the patients and the caregivers, during the interviews suggested to replace “supplement and amino-acid mixture” or “supplements” with “medical formula.” This wording was later changed to “medical food” to be consistent with the terminology used in current US published guidelines.

Conclusions

The translation of the UK English PKU-QOL questionnaire into US English did not raise critical semantic and cultural issues. The PKU-QOL will be valuable for US healthcare providers in individualizing treatment and managing patients with PKU.

Systematic Review and Meta-Analysis of Neuropsychiatric Symptoms and Executive Functioning in Adults With Phenylketonuria

This systematic review and meta-analysis (MA) investigates the impact of elevated blood phenylalanine (Phe) on neuropsychiatric symptoms in adults with phenylketonuria (PKU). The meta-analysis of PKU is challenging because high-quality evidence is lacking due to the limited number of affected individuals and few placebo-controlled, double-blind studies of adults with high and low blood Phe. Neuropsychiatric symptoms associated with PKU exceed general population estimates for inattention, hyperactivity, depression, and anxiety. High Phe is associated with an increased prevalence of neuropsychiatric symptoms and executive functioning deficits whereas low Phe is associated with improved neurological performance. Findings support lifelong maintenance of low blood Phe.

Updated, web-based nutrition management guideline for PKU: An evidence and consensus based approach

BACKGROUND

In 2014, recommendations for the nutrition management of phenylalanine hydroxylase deficiency were published as a companion to the concurrently published American College of Medical Genetics and Genomics guideline for the medical treatment of phenylketonuria (PKU). These were developed primarily from a summary of findings from the PKU scientific review conference sponsored by the National Institutes of Health and Agency for Healthcare Research & Quality along with additional systematic literature review. Since that time, the Genetic Metabolic Dietitians International and the Southeast Regional Newborn Screening and Genetics Collaborative have partnered to create a web-based technology platform for the update and development of nutrition management guidelines for inherited metabolic disorders.

OBJECTIVE

The purpose of this PKU guideline is to establish harmonization in treatment and monitoring, to guide the integration of nutrition therapy in the medical management of PKU, and to improve outcomes (nutritional, cognitive, and developmental) for individuals with PKU in all life stages while reducing associated medical, educational, and social costs.

METHODS

Six research questions critical to PKU nutrition management were formulated to support guideline development: Review, critical appraisal, and abstraction of peer-reviewed studies and unpublished practice literature, along with expert Delphi survey feedback, nominal group process, and external review from metabolic physicians and dietitians were utilized for development of recommendations relevant to each question. Recommendations address nutrient intake, including updated protein requirements, optimal blood phenylalanine concentrations, nutrition interventions, monitoring parameters specific to life stages, adjunct therapies, and pregnancy and lactation. Recommendations were graded using a rigorous system derived from the Academy of Nutrition and Dietetics.

RESULTS AND CONCLUSION

These guidelines, updated utilizing a thorough and systematic approach to literature analysis and national consensus process, are now easily accessible to the global community via the newly developed digital platform. For additional details on specific topics, readers are encouraged to review materials on the online portal: https://GMDI.org/.