Dual guidance structure for evaluation of patients with unclear diagnosis in centers for rare diseases (ZSE-DUO): study protocol for a controlled multi-center cohort study

Background

In individuals suffering from a rare disease the diagnostic process and the confirmation of a final diagnosis often extends over many years. Factors contributing to delayed diagnosis include health care professionals' limited knowledge of rare diseases and frequent (co-)occurrence of mental disorders that may complicate and delay the diagnostic process. The ZSE-DUO study aims to assess the benefits of a combination of a physician focusing on somatic aspects with a mental health expert working side by side as a tandem in the diagnostic process.

Study design

This multi-center, prospective controlled study has a two-phase cohort design.

Methods

Two cohorts of 682 patients each are sequentially recruited from 11 university-based German Centers for Rare Diseases (CRD): the standard care cohort (control, somatic expertise only) and the innovative care cohort (experimental, combined somatic and mental health expertise). Individuals aged 12 years and older presenting with symptoms and signs which are not explained by current diagnoses will be included. Data will be collected prior to the first visit to the CRD’s outpatient clinic (T0), at the first visit (T1) and 12 months thereafter (T2).

Outcomes

Primary outcome is the percentage of patients with one or more confirmed diagnoses covering the symptomatic spectrum presented. Sample size is calculated to detect a 10 percent increase from 30% in standard care to 40% in the innovative dual expert cohort. Secondary outcomes are (a) time to diagnosis/diagnoses explaining the symptomatology; (b) proportion of patients successfully referred from CRD to standard care; (c) costs of diagnosis including incremental cost effectiveness ratios; (d) predictive value of screening instruments administered at T0 to identify patients with mental disorders; (e) patients’ quality of life and evaluation of care; and f) physicians’ satisfaction with the innovative care approach.

Conclusions

This is the first multi-center study to investigate the effects of a mental health specialist working in tandem with a somatic expert physician in CRDs. If this innovative approach proves successful, it will be made available on a larger scale nationally and promoted internationally. In the best case, ZSE-DUO can significantly shorten the time to diagnosis for a suspected rare disease.

Trial registration ClinicalTrials.gov; Identifier: NCT03563677; First posted: June 20, 2018, https://clinicaltrials.gov/ct2/show/NCT03563677.

Identification and Affinity Determination of Protein-Antibody and Protein-Aptamer Epitopes by Biosensor-Mass Spectrometry Combination

Analytical methods for molecular characterization of diagnostic or therapeutic targets have recently gained high interest. This review summarizes the combination of mass spectrometry and surface plasmon resonance (SPR) biosensor analysis for identification and affinity determination of protein interactions with antibodies and DNA-aptamers. The binding constant (KD) of a protein-antibody complex is first determined by immobilizing an antibody or DNA-aptamer on an SPR chip. A proteolytic peptide mixture is then applied to the chip, and following removal of unbound material by washing, the epitope(s) peptide(s) are eluted and identified by MALDI-MS. The SPR-MS combination was applied to a wide range of affinity pairs. Distinct epitope peptides were identified for the cardiac biomarker myoglobin (MG) both from monoclonal and polyclonal antibodies, and binding constants determined for equine and human MG provided molecular assessment of cross immunoreactivities. Mass spectrometric epitope identifications were obtained for linear, as well as for assembled ("conformational") antibody epitopes, e.g., for the polypeptide chemokine Interleukin-8. Immobilization using protein G substantially improved surface fixation and antibody stabilities for epitope identification and affinity determination. Moreover, epitopes were successfully determined for polyclonal antibodies from biological material, such as from patient antisera upon enzyme replacement therapy of lysosomal diseases. The SPR-MS combination was also successfully applied to identify linear and assembled epitopes for DNA-aptamer interaction complexes of the tumor diagnostic protein C-Met. In summary, the SPR-MS combination has been established as a powerful molecular tool for identification of protein interaction epitopes.

Long-term Outcomes of Individuals With Metabolic Diseases Identified Through Newborn Screening

BACKGROUND

Although extended newborn screening (NBS) programs have been introduced more than 20 years ago, their impact on the long-term clinical outcome of individuals with inherited metabolic diseases (IMDs) is still rarely investigated.

METHODS

We studied the clinical outcomes of individuals with IMDs identified by NBS between 1999 and 2016 in a prospective multicenter observational study.

RESULTS

In total, 306 screened individuals with IMDs (115 with phenylketonuria and 191 with other IMDs with a lifelong risk for metabolic decompensation) were followed for a median time of 6.2 years. Although the risk for metabolic decompensation was disease-specific and NBS could not prevent decompensations in every individual at risk (n = 49), the majority did not develop permanent disease-specific signs (75.9%), showed normal development (95.6%) and normal cognitive outcome (87.7%; mean IQ: 100.4), and mostly attended regular kindergarten (95.2%) and primary school (95.2%). This demonstrates that not only individuals with phenylketonuria, serving as a benchmark, but also those with lifelong risk for metabolic decompensation had a favorable long-term outcome. High NBS process quality is the prerequisite of this favorable outcome. This is supported by 28 individuals presenting with first symptoms at a median age of 3.5 days before NBS results were available, by the absence of neonatal decompensations after the report of NBS results, and by the challenge of keeping relevant process parameters at a constantly high level.

CONCLUSIONS

NBS for IMDs, although not completely preventing clinical presentations in all individuals, can be considered a highly successful program of secondary prevention.

Extent, impact, and predictors of diagnostic delay in Pompe disease: A combined survey approach to unveil the diagnostic odyssey

BACKGROUND

Early diagnosis is of substantial benefit for patients with Pompe disease. Yet underdiagnosing and substantial diagnostic delay are still frequent and the determinants of this are unknown. This study is the first to systematically investigate the diagnostic odyssey in Pompe disease from patients', parents', and physicians' perspectives.

METHODS

Patients with infantile or late onset Pompe disease, their parents as well as their metabolic experts were invited to fill in respective surveys. The survey addressed perceived disease symptoms at onset and during the course of the disease, specialties of involved physicians, activities of patient-initiated search for diagnosis and the perceived impact of time to diagnosis on outcome. Results of experts' and patients'/parents' surveys were compared and expressed by descriptive statistics.

RESULTS AND DISCUSSION

We collected data on 15 males and 17 females including 9 infantile and 23 late onset Pompe patients. All received the correct diagnosis at a metabolic or musculoskeletal expert center. Patients with direct referral to the expert center had the lowest diagnostic delay, while patients who were seen by several physicians, received the correct diagnosis after 44%-200% longer delay. The proportion of direct referral varied strongly between pediatricians (57%) and other disciplines (18%-36%).

CONCLUSION

Our study highlights a substantially larger diagnostic delay in Pompe patients that are not directly referred to expert centers for diagnostic work. Our findings may be used to develop more successful strategies for early diagnosis.

SYNOPSIS

Diagnostic delay in Pompe disease is substantial particularly in patients that are not directly referred to expert centers for diagnostic workup, so facilitating direct referral may be a new strategy for early diagnosis.

Clinical onset and course, response to treatment and outcome in 24 patients with the cblE or cblG remethylation defect complemented by genetic and in vitro enzyme study data

BACKGROUND

The cobalamin E (cblE) (MTRR, methionine synthase reductase) and cobalamin G (cblG) (MTR, methionine synthase) defects are rare inborn errors of cobalamin metabolism leading to impairment of the remethylation of homocysteine to methionine.

METHODS

Information on clinical and laboratory data at initial full assessment and during the course of the disease, treatment, outcome and quality of life was obtained in a survey-based, retrospective study from physicians caring for patients with the CblE or CblG defect. In addition, data on enzyme studies in cultured skin fibroblasts and mutations in the MTRR and MTR gene were analysed.

RESULTS

In 11 cblE and 13 cblG patients, failure to thrive, feeding problems, delayed milestones, muscular hypotonia, cognitive impairment and macrocytic anaemia were the most frequent symptoms. Delay in diagnosis depended on age at first symptom and clinical pattern at presentation and correlated significantly with impaired communication abilities at follow-up. Eighteen/22 patients presented with brain atrophy or white matter disease. Biochemical response to treatment with variable combinations of betaine, cobalamin, folate was significant. The overall course was considered improving (n = 8) or stable (n = 15) in 96% of patients, however the average number of CNS symptoms per patient increased significantly over time and 16 of 23 patients were classified as developmentally delayed or severely handicapped. In vitro enzyme analysis data showed no correlation with outcome. Predominantly private mutations were detected and no genotype- phenotype correlations evident.

CONCLUSIONS

The majority of patients with the cblE and cblG defect show limited clinical response to treatment and have neurocognitive impairment.

Cross-sectional observational study of 208 patients with non-classical urea cycle disorders

Urea cycle disorders (UCDs) are inherited disorders of ammonia detoxification often regarded as mainly of relevance to pediatricians. Based on an increasing number of case studies it has become obvious that a significant number of UCD patients are affected by their disease in a non-classical way: presenting outside the newborn period, following a mild course, presenting with unusual clinical features, or asymptomatic patients with only biochemical signs of a UCD. These patients are surviving into adolescence and adulthood, rendering this group of diseases clinically relevant to adult physicians as well as pediatricians. In preparation for an international workshop we collected data on all patients with non-classical UCDs treated by the participants in 20 European metabolic centres. Information was collected on a cohort of 208 patients 50% of which were ≥ 16 years old. The largest subgroup (121 patients) had X-linked ornithine transcarbamylase deficiency (OTCD) of whom 83 were female and 29% of these were asymptomatic. In index patients, there was a mean delay from first symptoms to diagnosis of 1.6 years. Cognitive impairment was present in 36% of all patients including female OTCD patients (in 31%) and those 41 patients identified presymptomatically following positive newborn screening (in 12%). In conclusion, UCD patients with non-classical clinical presentations require the interest and care of adult physicians and have a high risk of neurological complications. To improve the outcome of UCDs, a greater awareness by health professionals of the importance of hyperammonemia and UCDs, and ultimately avoidance of the still long delay to correctly diagnose the patients, is crucial.

An unexpectedly high frequency of hypergalactosemia in an immigrant Bosnian population revealed by newborn screening

In galactokinase (GALK) deficiency, galactose cannot be phosphorylated into galactose-1-phosphate, which leads to cataract formation. Neonatal screening for hypergalactosemia in Berlin has been performed by thin-layer chromatography since 1978, which detects classical galactosemia and GALK deficiency. Until 1991, GALK deficiency has not been identified in a total of approximately 260,000 samples. In contrast, from 1992 to 1999, nine patients were detected in a total of approximately 240,000 screened newborns. One Turkish patient was homozygous for two novel S142I/G148C GALK mutations in close proximity to the putative ATP-binding site of the enzyme. The other eight children were born to five families belonging to the Bosnian refugee population consisting of approximately 30,000 individuals who have arrived in Berlin since 1991. In two of these families, GALK deficiency was subsequently diagnosed in siblings who had cataract surgery at 4 and 5 y of age, respectively. In all these 10 Bosnian patients, a homozygous P28T mutation located near the active center of the enzyme was identified. We propose that neonatal screening of populations with a significant proportion of Bosnians and possibly other southeastern Europeans, e.g. Romani, should be particularly directed toward GALK deficiency, an inborn error of metabolism that is readily amenable to effective treatment.