Citations

Krabbe disease (KD) is a rare, inherited leukodystrophy associated with early mortality. Infantile Krabbe disease (IKD) was added to the Recommended Uniform Screening Panel (RUSP) in July 2024. Since then, U.S. states have continued to evaluate implementing KD newborn screening (NBS), and RUSP inclusion has hastened adoption efforts. This study aimed to characterize NBS program responses to this recommendation and identify factors influencing adoption and implementation. A mixed-methods approach was used, including a case review of Wisconsin’s process to add conditions to its NBS panel and a cross-sectional survey of U.S. NBS programs. Responses were obtained from 50 of 51 NBS programs. Twenty-two programs actively screen for KD, with ten additional programs in the implementation process. Screening approaches varied, particularly in psychosine (PSY) cutoff thresholds and testing algorithms. Programs reported a range of adoption pathways, including legislative mandates, advisory committee review, and state-specific nomination processes. Key factors impacting KD NBS adoption included uncertainty regarding treatment safety, efficacy, and availability, ethical considerations related to identifying later-onset disease, and logistical challenges such as laboratory readiness and clinical follow-up resources. This study provides a contemporary overview of national implementation of KD NBS and offers practical insights for programs considering adoption.

Newborn screening (NBS) for inborn errors of metabolism is challenged by high false-positive rates, which may lead to parental anxiety and increased healthcare costs associated with diagnostic follow-up. False-positive results often arise from changes in metabolite concentrations that mimic metabolic disorders as a consequence of differences in perinatal factors or nutritional status. To address this, Collaborative Laboratory Integrative Reports (CLIR) and the associated post-analytical tools (PATs) using multivariate interpretation and covariate-adjusted reference intervals may be used to improve specificity of NBS algorithms. In the current study, we examined whether CLIR can be applied to optimize the Dutch NBS program by reducing the false-positive rates. We developed and validated a CLIR-based PAT for CPT1 deficiency, GA-I, IVA and MSUD within the Dutch NBS program. Single-condition tools (SCTs) and multivariate approaches, including marker ratios and covariate adjustments, were evaluated for their ability to discriminate true- and false-positive referrals. For CPT1 deficiency, age-adjusted SCT combined with birthweight, location correction, and the C18:1/methionine ratio substantially reduced false positives. For GA-I, C3DC-based ratios improved specificity while preserving true-positive detection, potentially reflecting postnatal renal immaturity in some cases. For IVA, the dual scatter plot fully separated true- and false-positive referrals, highlighting the limitations of single-marker screening. For MSUD, differences between false-positive and true-positive cases were more pronounced, yet a similar number of false positives were still referred; valine-related markers contributed to false positives, while leucine and the Xle/Phe ratio better identified true positives. CLIR-based post-analytical tools enhanced NBS specificity through covariate-aware, multivariate interpretation. This provides important input for decision makers in both the Dutch NBS, as well as the NBS community worldwide.

Since October 2019, screening for methylmalonic acidemia (MMA) has been implemented in the Dutch Newborn Screening (NBS) program. Since implementation, most referrals for MMA have been the result of (maternal) vitamin B12 deficiency. Although vitamin B12 deficiency is an important condition and early detection can confer health benefits, its identification was not the original objective of the screening. We therefore examined whether genetic forms of MMA can be distinguished from acquired forms. Early distinction between these forms is essential for guiding clinical management, informing prognosis, and enabling appropriate genetic counseling. Specifically, we tested whether the use of Collaborative Laboratory Integrated Reports (CLIR) to complement NBS results improved specificity of the test for genetic MMAs. We found that with the use of CLIR, genetic conditions including methylmalonyl-CoA mutase (mut) deficiency and cobalamin (cbl) A, B, C and D deficiency can be partially differentiated from acquired causes. This results in a significant reduction in the number of second-tier tests required. However, this approach may also exclude certain other genetic causes. Based on all findings, we provide considerations and implications for MMA screening that may inform decision-makers in (other) NBS programs.

COASY-related disorders (CRDs) are a spectrum of autosomal recessive conditions caused by the dysfunction of CoA synthase, an enzyme responsible for the final steps of CoA synthesis. Clinical manifestations of CRDs are highly variable, ranging from perinatal lethal pontocerebellar hypoplasia to childhood-onset neurodegenerative brain iron accumulation, which is often recognized after clinical regression. Recent reports have described a few individuals with CRD who screened positive for carnitine palmitoyltransferase-I deficiency by newborn screening (NBS). However, heterogeneous clinical presentations, conflicting biochemical/molecular sequencing of CPT1A, and a lack of metabolic characterization have led to lengthy, costly diagnostic journeys. To address some of these aspects, this investigation retrospectively evaluated NBS acylcarnitine patterns in five CRD cases using Collaborative Laboratory Integrated Reports (CLIR). A total of 25 metabolites/ratios were identified to deviate significantly from reference ranges and were primarily composed of elevated free carnitine and reduced long-chain acylcarnitine levels. While low acylcarnitine concentrations are often not reported due to a lack of lower reference cutoffs, ratios involving these metabolites relative to short-chain acylcarnitines could aid in identifying CRD cases via NBS. When comparing this pattern to CPT-Ia cases, we confirmed a nearly identical acylcarnitine pattern between these, and thus support the need to consider CRD in cases with NBS results suggestive of CPT-Ia. This study is the first case series to characterize NBS patterns in patients with CRD and highlights the unique opportunity for early detection, particularly in cases that are neonatally asymptomatic and have unremarkable confirmatory biochemical results.

Background/Objectives: Dutch newborn screening is an important public health program designed to detect conditions early in life, enabling timely interventions that can prevent mortality, morbidity, and long-term disabilities. However, the program also faces certain challenges. One such issue is obtaining and maintaining a high positive predictive value (PPV); another is that newborn screening (NBS) in the Netherlands is intended for all newborn babies until the age of six months. This means comparing infants at different ages may introduce variability that complicates data interpretation. To support the optimization of the program, we systematically analyzed population-level tandem mass spectrometry (MS/MS) data to explore postnatal metabolic changes. Methods: We evaluated the impact of covariates—including birth weight, gestational age, age at blood collection, and biological sex—on metabolite profiles using retrospective newborn screening (NBS) data. Special emphasis was placed on the combined effects of these covariates. The analysis was based on data from 985,629 newborns collected between 2018 and 2024. Results: Specifically, (extremely) preterm infants exhibit altered levels of several amino acids and acylcarnitines. Moreover, we observed multiplicative effects of gestational age and birth weight on several metabolic markers. Biological sex however, does not have an impact. The largest impact of the age of sampling was observed on the C0/C16+C18 ratio, which may impact screening performance for CPT1 deficiency. Conclusions: Covariate-adjusted reference values could improve the performance of the Dutch newborn screening.