Collaborative evaluation study on 18 candidate diseases for newborn screening in 1.77 million samples

Analytical and therapeutic innovations led to a continuous but variable extension of newborn screening (NBS) programmes worldwide. Every extension requires a careful evaluation of feasibility, diagnostic (process) quality and possible health benefits to balance benefits and limitations. The aim of this study was to evaluate the suitability of 18 candidate diseases for inclusion in NBS programmes. Utilising tandem mass spectrometry as well as establishing specific diagnostic pathways with second-tier analyses, three German NBS centres designed and conducted an evaluation study for 18 candidate diseases, all of them inherited metabolic diseases. In total, 1 777 264 NBS samples were analysed. Overall, 441 positive NBS results were reported resulting in 68 confirmed diagnoses, 373 false-positive cases and an estimated cumulative prevalence of approximately 1 in 26 000 newborns. The positive predictive value ranged from 0.07 (carnitine transporter defect) to 0.67 (HMG-CoA lyase deficiency). Three individuals were missed and 14 individuals (21%) developed symptoms before the positive NBS results were reported. The majority of tested candidate diseases were found to be suitable for inclusion in NBS programmes, while multiple acyl-CoA dehydrogenase deficiency, isolated methylmalonic acidurias, propionic acidemia and malonyl-CoA decarboxylase deficiency showed some and carnitine transporter defect significant limitations. Evaluation studies are an important tool to assess the potential benefits and limitations of expanding NBS programmes to new diseases.

Combined Newborn Screening Allows Comprehensive Identification also of Attenuated Phenotypes for Methylmalonic Acidurias and Homocystinuria

Newborn screening (NBS) programs are effective measures of secondary prevention and have been successively extended. We aimed to evaluate NBS for methylmalonic acidurias, propionic acidemia, homocystinuria, remethylation disorders and neonatal vitamin B12 deficiency, and report on the identification of cofactor-responsive disease variants. This evaluation of the previously established combined multiple-tier NBS algorithm is part of the prospective pilot study "NGS2025" from August 2016 to September 2022. In 548,707 newborns, the combined algorithm was applied and led to positive NBS results in 458 of them. Overall, 166 newborns (prevalence 1: 3305) were confirmed (positive predictive value: 0.36); specifically, methylmalonic acidurias (N = 5), propionic acidemia (N = 4), remethylation disorders (N = 4), cystathionine beta-synthase (CBS) deficiency (N = 1) and neonatal vitamin B12 deficiency (N = 153). The majority of the identified newborns were asymptomatic at the time of the first NBS report (total: 161/166, inherited metabolic diseases: 9/14, vitamin B12 deficiency: 153/153). Three individuals were cofactor-responsive (methylmalonic acidurias: 2, CBS deficiency: 1), and could be treated by vitamin B12, vitamin B6 respectively, only. In conclusion, the combined NBS algorithm is technically feasible, allows the identification of attenuated and severe disease courses and can be considered to be evaluated for inclusion in national NBS panels.

Health Outcomes of Infants with Vitamin B12 Deficiency Identified by Newborn Screening and Early Treated

OBJECTIVE

To evaluate the clinical outcomes at age 1.5 ± 0.5 years of infants with vitamin B₁₂ deficiency identified by newborn screening (NBS).

STUDY DESIGN

Prospective multicenter observational study on health outcomes of 31 infants with vitamin B₁₂ deficiency identified by NBS. Neurodevelopment was assessed by the Denver Developmental Screening Test.

RESULTS

In 285 862 newborns screened between 2016 and 2019, the estimated birth prevalence of vitamin B₁₂ deficiency was 26 in 100 000 newborns, with high seasonal variations (lowest in summer: 8 in 100 000). Infants participating in the outcome study (N = 31) were supplemented with vitamin B₁₂ for a median (range) of 5.9 (1.1-16.2) months. All achieved age-appropriate test results in Denver Developmental Screening Test at age 15 (11-23) months and did not present with symptoms characteristic for vitamin B₁₂ deficiency. Most (81%, n = 25) mothers of affected newborns had a hitherto undiagnosed (functional) vitamin B₁₂ deficiency, and, subsequently, received specific therapy.

CONCLUSIONS

Neonatal vitamin B₁₂ deficiency can be screened by NBS, preventing the manifestation of irreversible neurologic symptoms and the recurrence of vitamin B₁₂ deficiency in future pregnancies through adequate treatment of affected newborns and their mothers. The high frequency of mothers with migrant background having a newborn with vitamin B₁₂ deficiency highlights the need for improved prenatal care.

Implementing a tracking system for confirmatory diagnostic results after positive newborn screening for cystic fibrosis-implications for process quality and patient care

Newborn screening for cystic fibrosis (CF-NBS) was introduced in Germany in 2016. Currently, systematic follow-up of positive CF-NBS results is not implemented or reimbursed in the NBS program. We investigated results of confirmatory testing over 24 months after implementation of CF-NBS for a large German NBS center before and after introduction of an active tracking system and performed a cost calculation for tracking. Results are compared with the federal state of Bavaria, where a centralized tracking system has been in place for many years. At the NBS center, 244 of 281,907 children had a positive CF-NBS result requiring diagnostic confirmation. Before implementation of a telephone tracking system, only 43% of confirmatory results were returned despite repeated written requests. The consecutive strategy including telephone tracking led to an increase of resolved cases to 84%. However, the centralized tracking system in Bavaria, assigning children with positive CF-NBS directly to a responsible CF-center, resolved 99% of cases. The calculated additional cost for a tracking system in Germany including telephone tracking is 1.20€ per newborn screened.Conclusion: The implementation of a tracking system achieves a distinct improvement in CF-NBS with justifiable costs. The effect can be limited by absence of centralized organization of confirmatory testing. What is Known: • Newborn screening for cystic fibrosis (CF-NBS) has been performed for many years in several countries worldwide • While many studies have focused on different CF-NBS strategies, the organization of confirmatory testing and process quality concerning returned information to the NBS center has so far received less attention. What is New: • The implementation of an active tracking system achieves a distinct improvement of clarified cases after positive CF-NBS with justifiable costs. • The effect of a tracking system can be limited by the absence of a centralized organization of confirmatory testing.

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.

Newborn Screening for Vitamin B12 Deficiency in Germany-Strategies, Results, and Public Health Implications

OBJECTIVE

To evaluate a systematic newborn screening (NBS) strategy for vitamin B₁₂ deficiency.

STUDY DESIGN

In a prospective single-center NBS study, a systematic screening strategy for vitamin B₁₂ deficiency was developed and evaluated. Tandem-mass spectrometry screening was complemented by 2 second-tier strategies, measuring methylmalonic/3-OH-propionic/methylcitric acid, and homocysteine from dried blood spots.

RESULTS

In a cohort of 176 702 children screened over 27 months, 33 children were detected by NBS in whom (maternal) vitamin B₁₂ deficiency was confirmed. Homocysteine was the most sensitive marker for vitamin B₁₂ deficiency, but only combination with a second-tier strategy evaluating methylmalonic acid allowed for detection of all 33 children. Mothers were of various ethnic origins, and 89% adhered to a balanced diet. Treatment in children was performed predominantly by oral vitamin B₁₂ supplementation (84%), and all children remained without clinical symptoms at short-term follow-up.

CONCLUSIONS

Vitamin B₁₂ deficiency is a treatable condition but can cause severe neurologic sequelae in infants if untreated. The proposed screening strategy is feasible and effective to identify moderate and severe cases of vitamin B₁₂ deficiency. With an incidence of 1:5355 newborns, vitamin B₁₂ deficiency is more frequent than inborn errors of metabolism included in NBS panels. Treatment of vitamin B₁₂ deficiency is easy, and additional benefits can be achieved for previously undiagnosed affected mothers. This supports inclusion of vitamin B₁₂ deficiency into NBS but also stresses the need for increased awareness of vitamin B₁₂ deficiency in caregivers of pregnant women.

High incidence of maternal vitamin B12 deficiency detected by newborn screening: first results from a study for the evaluation of 26 additional target disorders for the German newborn screening panel

BACKGROUND

Newborn screening (NBS) in Germany currently includes 15 target disorders. Recent diagnostic improvements suggest an extension of the screening panel.

METHODS

Since August 2016, a prospective study evaluating 26 additional target disorders (25 metabolic disorders and vitamin B₁₂-deficiency) in addition to the German screening panel is performed at the Newborn Screening Center Heidelberg. First-tier results from tandem-MS screening are complemented by second-tier strategies for 15 of the additional target disorders. NBS results of seven patients diagnosed symptomatically with one of the additional target disorders by selective screening since August 2016 are retrospectively evaluated.

RESULTS

Over a 13-month period, 68,418 children participated in the study. Second-tier analyses were performed in 5.4% of samples. Only 59 (0.1%) of study participants had abnormal screening results for one of the additional target disorders. Target disorders from the study panel were confirmed in 12 children: 1 3-hydroxy-3-methylglutaryl coenzyme A (CoA)-lyase deficiency, 1 citrullinemia type I, 1 multiple acyl-CoA dehydrogenase-deficiency, 1 methylenetetrahydrofolate reductase-deficiency, and 8 children with maternal vitamin B₁₂-deficiency. In addition, six of seven patients diagnosed symptomatically outside the study with one of the target disorders would have been identified by the study strategy in their NBS sample.

CONCLUSIONS

Within 13 months, the study "Newborn Screening 2020" identified additional 12 children with treatable conditions while only marginally increasing the recall rate by 0.1%. Maternal vitamin B₁₂-deficiency was the most frequent finding. Even more children could benefit from screening for the additional target disorders by extending the NBS panel for Germany and/or other countries.

Newborn screening for remethylation disorders and vitamin B12 deficiency-evaluation of new strategies in cohorts from Qatar and Germany

BACKGROUND

Newborn screening is a precondition for early diagnosis and successful treatment of remethylation disorders and classical homocystinuria (cystathionine-ß-synthase deficiency). Newborn screening for classical homocystinuria using total homocysteine measurement in dried blood spots has been very successfully performed for many years for newborns from Qatar.

METHODS

A new optimized newborn screening strategy for remethylation disorders and homocystinuria was developed and evaluated for newborns from Qatar using total homocysteine measurement as first-tier and methionine, methionine-phenylalanine-ratio and propionylcarnitine as second-tiers. Proposed cut-offs were also retrospectively evaluated in newborn screening samples of 12 patients with remethylation disorders and vitamin B₁₂ deficiency from Qatar and Germany.

RESULTS

Over a 12 months period, the proposed strategy led to a decrease in the recall rate in homocysteine screening for Qatar from 1.09% to 0.68%, while allowing for additional systematic inclusion of remethylation disorders and vitamin B₁₂ deficiency into the screening panel for Qatar. In the evaluated period the applied strategy would have detected all patients with classical homocystinuria identified by the previous strategy and in addition 5 children with maternal nutritional vitamin B₁₂ deficiency and one patient with an isolated remethylation disorder. Additional retrospective evaluation of newborn screening samples of 12 patients from Germany and Qatar with remethlyation disorders or vitamin B₁₂ deficiency showed that all of these patients would have been detected by the cut-offs used in the proposed new strategy. In addition, an adapted strategy for Germany using methionine, methionine-phenylalanine-ratio and propionylcarnitine as first-tier, and homocysteine as a second-tier test was also positively evaluated retrospectively.

CONCLUSIONS

The proposed strategy for samples from Qatar allows inclusion of remethylation disorders and vitamin B₁₂ deficiency in the screening panel, while lowering the recall rate. An adapted second-tier strategy is presented for screening in Germany and will be prospectively evaluated over the next years in a pilot project named "Newborn Screening 2020".

Genetic cause and prevalence of hydroxyprolinemia

BACKGROUND

Hydroxyprolinemia is an inborn error of amino acid degradation that is considered a non-disease. Known for more than 50 years, its genetic cause and prevalence have remained unclear. In MS/MS newborn screening, the mass spectrum of hydroxyproline cannot be differentiated from isoleucine and leucine causing false positive newborn screening test results for maple syrup urine disease (MSUD).

METHODS

We studied two siblings with hydroxyprolinemia via exome sequencing and confirmed the candidate gene in five further individuals with hydroxyprolinemia, who were all characterized biochemically and clinically. The prevalence was calculated based on the number of individuals with hydroxyprolinemia detected via MS/MS newborn screening at our centre from 2003 to 2014.

RESULTS

In six cases, we identified homozygous or compound heterozygous mutations in PRODH2 as the underlying genetic cause of hydroxyprolinemia. One individual was heterozygous for a deletion in PRODH2 and had an intermittent biochemical phenotype with partial normalization of hydroxyproline concentrations. In one further individual with persistent hydroxyprolinemia no mutation in PRODH2 was found, raising the possibility of another defect of hydroxyproline degradation yet to be identified as the underlying cause of hydroxyprolinemia. Plasma hydroxyproline concentrations were clearly elevated in all individuals with biallelic mutations in PRODH2. All studied individuals remained asymptomatic, giving further evidence that hydroxyprolinemia is a benign condition. The estimated prevalence of hydroxyprolinemia in Germany is about one in 47,300 newborns.

CONCLUSION

Our results establish mutations in PRODH2 as a cause of human hydroxyprolinemia via impaired dehydrogenation of hydroxyproline to delta1-pyroline-3-hydroxy-5-carboxylic acid, and we suggest PRODH2 be renamed HYPDH. Hydroxyprolinemia is an autosomal-recessively inherited benign condition. It is a frequent cause of false positive screening results for MSUD, the prevalence being about 2.5 times higher than that of MSUD.

Medium-Chain Acyl-CoA Dehydrogenase Deficiency: Evaluation of Genotype-Phenotype Correlation in Patients Detected by Newborn Screening

BACKGROUND

Medium-chain acyl-CoA dehydrogenase deficiency (MCADD) is included in many newborn screening programmes worldwide. In addition to the prevalent mutation c.985A>G in the ACADM gene, potentially mild mutations like c.199T>C are frequently found in screening cohorts. There is ongoing discussion whether this mutation is associated with a clinical phenotype.

METHODS

In 37 MCADD patients detected by newborn screening, biochemical phenotype (octanoylcarnitine (C8), ratios of C8 to acetylcarnitine (C2), decanoylcarnitine (C10) and dodecanoylcarnitine (C12) at screening and confirmation) and clinical phenotype (inpatient emergency treatment, metabolic decompensations, clinical assessments, psychometric tests) were assessed in relation to genotype.

RESULTS

16 patients were homozygous for c.985A>G (group 1), 11 compound heterozygous for c.199T>C and c.985A>G/another mutation (group 2) and 7 compound heterozygous for c.985A>G and mutations other than c.199T>C (group 3) and 3 carried neither c.985A>G nor c.199T>C but other known homozygous mutations (group 4). At screening C8/C2 and C8/C10, at confirmation C8/C2, C8/C10 and C8/C12 differed significantly between patients compound heterozygous for c.199T>C (group 2) and other genotypes. C8, C10 and C8/C2 at screening were strongly associated with time of sampling in groups 1 + 3 + 4, but not in group 2. Clinical phenotype did not differ between genotypes. Two patients compound heterozygous for c.199T>C and a severe mutation showed neonatal decompensation with hypoglycaemia.

CONCLUSION

Biochemical phenotype differs between MCADD patients compound heterozygous for c.199T>C with a severe mutation and other genotypes. In patients detected by newborn screening, clinical phenotype does not differ between genotypes following uniform treatment recommendations. Neonatal decompensation can also occur in patients with the presumably mild mutation c.199T>C prior to diagnosis.

Efficacy and outcome of expanded newborn screening for metabolic diseases--report of 10 years from South-West Germany

BACKGROUND

National newborn screening programmes based on tandem-mass spectrometry (MS/MS) and other newborn screening (NBS) technologies show a substantial variation in number and types of disorders included in the screening panel. Once established, these methods offer the opportunity to extend newborn screening panels without significant investment and cost. However, systematic evaluations of newborn screening programmes are rare, most often only describing parts of the whole process from taking blood samples to long-term evaluation of outcome.

METHODS

In a prospective single screening centre observational study 373 cases with confirmed diagnosis of a metabolic disorder from a total cohort of 1,084,195 neonates screened in one newborn screening laboratory between January 1, 1999, and June 30, 2009 and subsequently treated and monitored in five specialised centres for inborn errors of metabolism were examined. Process times for taking screening samples, obtaining results, initiating diagnostic confirmation and starting treatment as well as the outcome variables metabolic decompensations, clinical status, and intellectual development at a mean age of 3.3 years were evaluated.

RESULTS

Optimal outcome is achieved especially for the large subgroup of patients with medium-chain acyl-CoA dehydrogenase deficiency. Kaplan-Meier-analysis revealed disorder related patterns of decompensation. Urea cycle disorders, organic acid disorders, and amino acid disorders show an early high and continuous risk, medium-chain acyl-CoA dehydrogenase deficiency a continuous but much lower risk for decompensation, other fatty acid oxidation disorders an intermediate risk increasing towards the end of the first year. Clinical symptoms seem inevitable in a small subgroup of patients with very early disease onset. Later decompensation can not be completely prevented despite pre-symptomatic start of treatment. Metabolic decompensation does not necessarily result in impairment of intellectual development, but there is a definite association between the two.

CONCLUSIONS

Physical and cognitive outcome in patients with presymptomatic diagnosis of metabolic disorders included in the current German screening panel is equally good as in phenylketonuria, used as a gold standard for NBS. Extended NBS entails many different interrelated variables which need to be carefully evaluated and optimized. More reports from different parts of the world are needed to allow a comprehensive assessment of the likely benefits, harms and costs in different populations.

Newborn population screening for classic homocystinuria by determination of total homocysteine from Guthrie cards

OBJECTIVE

To allow early recognition of cystathionine beta-synthase by newborn screening.

STUDY DESIGN

Total homocysteine was determined in dried blood spots with a novel, robust high-performance liquid chromatography method with tandem mass spectrometry. Quantification of homocysteine was linear over a working range up to 50 micromol/L. For mutation analysis, DNA was tested for 2 mutations common in Qatar.

RESULTS

Both methods proved to be suitable for high throughput processing. In 2 years, 7 infants with classic homocystinuria were identified of 12,603 native Qatari infants, yielding an incidence of 1:1800. Molecular screening would have missed 1 patient homozygous for a mutation not previously identified in the Qatari population. Over a period of 3 years, a total of 14 cases of classic homocystinuria were detected by screening of homocysteine from all newborn infants born in Qatar (n = 46 406). Homocysteine was always elevated, whereas methionine was elevated in only 7 cases.

CONCLUSIONS

The study offers a reliable method for newborn screening for cystathionine beta-synthase deficiency, reaching a sensitivity of up to 100%, even if samples are taken within the first 3 days of life.

Implementation of extended neonatal screening and a metabolic unit in the State of Qatar: developing and optimizing strategies in cooperation with the Neonatal Screening Center in Heidelberg

Qatar is a country in the Gulf area and member of the Gulf Cooperation Council states. The country is populated by original Qatari tribes that amount to about 200,000 people and about 600,000 expatriates mainly from Arabic and Asian countries. Inbreeding over centuries and high rates of consanguinity in the Qatari population and in some groups of expatriates, in addition to large family sizes and rapid population growth, have contributed to a high frequency of autosomal recessive disorders. In December 2003 Hamad Medical Corporation in Doha and the University Children's Hospital of Heidelberg, Germany, started an extended state-wide neonatal screening programme for metabolic and endocrine disorders, with the laboratory situated in Heidelberg, Germany. All aspects of the screening process had to be adapted to the unique situation of the laboratory being 6000 km from the birthplace of the neonates. Within 32 months, samples of 25,214 neonates were screened. In 28 cases an endocrine or metabolic diagnosis was identified (incidence 1:901, in Germany 1:1728). In particular, a variety of monogenic metabolic diseases were prevalent, with 19 patients detected giving an incidence of metabolic diseases of 1:1327 (Germany 1:2517). Each euro spent on the screening programme saved more than 25 euros in health and social costs. The programme revealed a high incidence of treatable inborn metabolic diseases in the population of Qatar. A reliable screening for classical homocystinuria showing a unique incidence of >1:3000 and for sickle cell disease has now been added.

Neonatal screening for glutaric aciduria type I: strategies to proceed

Acute encephalopathic crisis in glutaric aciduria type I results in an unfavourable disease course and poor outcome, dominated by dystonia, feeding problems, seizures and reduced life expectancy. A conditio sine qua non for the prevention of irreversible brain damage is timely diagnosis and start of therapy, i.e. before the onset of neurological disease. As there are no specific clinical signs or symptoms that allow a reliable detection of these patients before the manifestation of encephalopathic crises, neonatal screening programmes for glutaric aciduria type I have been established in some countries using analysis of glutarylcarnitine in dried blood spots by tandem mass spectrometry. This article summarizes recent strategies, pitfalls and shortcomings of mass screening for glutaric aciduria type I, focusing on the relevant risk of missing patients with a mild biochemical phenotype (i.e. low excretors). Furthermore, it evaluates a binary strategy--using glutarylcarnitine as primary variable and glutarylcarnitine/acylcarnitine ratios as secondary variable--to improve the diagnostic sensitivity and specificity of neonatal screening for glutaric aciduria type I. An optimization of diagnostic as well as therapeutic procedures must be achieved before screening for glutaric aciduria type I can be regarded as reliable and beneficial for all patients.