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.

Riboflavin (RF, vitamin B2) is an essential vitamin of which the co-factors are critical to numerous cellular processes. RF is used as a treatment for inherited metabolic diseases (IMDs), although its effectiveness in many disorders has not been established. We aim to summarize all available data on the efficacy and safety of RF in the management of IMDs. A systematic literature search was conducted for articles reporting the effectiveness of RF in IMDs. RF therapy was considered "effective" in an IMD if more than 75% of patients showed a positive response, "uncertain" in case of a positive response in fewer than 75% of patients, and "not effective" if patients deteriorated or died following RF therapy. RF therapy was reported in 381 articles addressing 33 separate IMDs. A positive effect was established in MADD type 3 (n=536, 93.1% responsive), RTD 2,3 (n = 94, 90.4% responsive), ACAD 9 (n = 29, 75.9% responsive), and FAD transporter deficiency (n = 5, 100% responsive). The effect was uncertain in complex I and II deficiency, ethylmalonic encephalopathy, FAD synthase deficiency, glutaric aciduria type 1, L2 hydroxyglutaric aciduria, and MADD type 2. RF was not effective in MADD type 1. Adverse effects were infrequent and mild. RF therapy in MADD type 3, RTD 2 and 3, ACAD9, and FAD transporter deficiency is safe and effective. Access to RF for these patients is crucial. For a substantial group of IMDs, the effect of RF remains uncertain. In these conditions, a trial of RF therapy with clearly defined outcome criteria might be considered.

Recent advances in molecular biology and genomics have significantly enhanced our understanding of rare diseases. While enabling the development of highly targeted therapies, it also leads to complexity in the development, regulation, and accessibility of orphan medicines. Unmet need and great promise of new medicines, combined with high prices and uncertain effectiveness, highlight the shortcomings of the system, particularly evident for highly specialized treatment options, such as advanced therapy medicinal products and RNA-based treatments. While all stakeholders in this field must take responsibility, academic researchers and clinicians have a vital role which must be strengthened to improve access to and affordability of medicines. Regarding academia-driven orphan medicine development, academic contributions are predominantly concentrated in the early research phases, often lacking continuity throughout the full development pipeline. There is limited expertise in regulatory affairs and market access, and little involvement in medicine pricing or licensing negotiations. Recommendations include sustained academic engagement across all development stages, integration of regulatory and market access training into educational programs, and the implementation of socially responsible frameworks. Strategies promoting the rational use of orphan medicines should be embedded across the entire product lifecycle. Industry-driven development typically interacts primarily with regulatory agencies and payers, with academia playing a reactive and, at times, conflicted role. Independent academic-industry interaction is recommended, with early involvement in clinical trial design. Additionally, academia should proactively contribute to the evaluation of new therapies, development of controlled access models, and exploration of sustainable pricing frameworks. Establishing independent, multi-purpose disease registries would enhance post-authorization monitoring and evidence generation.

In the Netherlands, the newborn screening (NBS) program includes screening for propionic aciduria (PA) and methylmalonic aciduria (MMA). When initial screening reveals elevated C3 concentrations or abnormal ratios (C3/C2, C3/C16), a second-tier test measuring methylcitric acid (MCA) for PA and methylmalonic acid (MMAmb) for MMA is performed. While this two-tier approach reduces false positives effectively, it can delay referral from the NBS program and diagnosis of propionic aciduria. We describe four early-onset PA cases in which the current Dutch screening algorithm negatively impacted clinical outcomes, highlighting the need for expedited referral. We investigated different alternative screening strategies to identify the most effective approach for improving timeliness, while maintaining the high specificity of Dutch PA NBS. This revised approach prioritizes the evaluation of the C3/C2 ratio in first-tier screening. Specifically, samples with a C3/C2 ratio ≥ 0.75 should be referred directly for medical consultation and confirmatory testing. For all other samples with less pronounced biochemical abnormalities, the existing two-tier screening algorithm remains an appropriate NBS protocol. To position our approach internationally, a survey of European NBS programs was conducted to compare screening and referral protocols for PA across the region.

Currently, Dutch newborns are screened for tyrosinemia type 1 (TT1) using succinylacetone (SA) as the biomarker. Although the sensitivity of the test is high, a high number of false positives is observed. Here, the aim is to evaluate the current Dutch newborn-screening protocol and to assess alternatives, specifically the use of biomarkers that are already being measured, to increase the positive predictive value (PPV). TT1 screening was performed with the Revvity NeoBase assay between 2008 and 2017, and since 2018, the Revvity NeoBase 2 assay has been used. Data from 2018 to 2021 were used for evaluation. To simulate alternative screening protocols, these data were enriched with results of referrals from other periods and a false negative (FN) from 2010. In 2018-2021, 693,821 newborns were screened, resulting in 23 referrals, of whom two were TT1 patients. For this period, to date, no FN have been reported, resulting in a provisional sensitivity of 100%, a specificity of 99.997%, and a PPV and negative predictive value of 9% and 100%, respectively. To improve the PPV, we combined SA, tyrosine (tyr), tyr × SA and tyr/phenylalanine and achieved a PPV of 72% for this dataset without introducing FN in the original dataset. This illustrates that future screening for TT1 may benefit from the addition of these biomarkers.

In 2007, the Dutch newborn screening (NBS) program was expanded to include C5-OH as a marker to screen for three inborn errors of metabolism (IEMs): 3-methylcrotonyl-CoA carboxylase deficiency (3-MCCD), 3-hydroxy-3-methylglutaryl-CoA lyase deficiency (HMGCLD) and holocarboxylase synthetase deficiency (HLCSD). This study evaluates the effectiveness of C5-OH as an NBS marker by analyzing data from neonates screened in the Dutch NBS program from 2007 to 2023 and by reviewing the literature on various IEMs detected by an elevated NBS C5-OH concentration worldwide. Of the 126 neonates referred on the basis of elevated C5-OH concentrations in the Netherlands, 46 were true positive cases. No missed cases in the Netherlands have been reported so far, resulting in a positive predictive value of 38.3% and a negative predictive value of 100%. Strikingly, there was notable overlap between C5-OH concentrations of true and false positive cases. The systematic review included 58 articles and showed that C5-OH concentrations of patients with different IEMs reported in the literature were insufficiently distinctive to differentiate between these diseases. While C5-OH can be used to detect patients with 3-MCCD, HCLSD, and HMGCLD, its value is limited by the overlap of C5-OH concentrations between affected and unaffected neonates and among patients with different diseases. This emphasizes the need for improvement of the screening strategy and potentially the use of additional markers to increase its specificity.

Movement disorders are common in inherited metabolic diseases (IMDs) and significantly impact quality of life. Unfortunately, they are often underrecognised by metabolic physicians. This study investigated whether a new screening tool improves recognition of movement disorders in IMD patients by non-neurologists. Internists and paediatricians specialized in IMDs assessed videos of 44 IMD patients who perform four specific neurological tests, to evaluate the presence and phenotype of a movement disorder. Initially, baseline assessments were performed without the tool. Eight months later, the same videos were assessed using an instructional video demonstrating the four neurological tests, and a screening tool including these tests with 14 yes/no questions regarding observed abnormalities. One hundred and forty-nine assessments were conducted by 15 metabolic internists and paediatricians. At baseline, 70% (105/149) of assessments correctly determined the presence of a movement disorder. Sensitivity of the tool was 68%. In the second measurement, when the outcome of the tool was considered decisive (with at least one positive answer indicating a movement disorder), 79% (117/149) of assessments were correct. Sensitivity of the tool increased to 87% (Chi-square = 15.75, p < 0.001). All severe and moderately severe movement disorders were recognized in the second measurement. The tool and instructional video did not enhance recognition of specific movement disorder phenotypes. However, the tool did improve the accuracy of treatment indications (chi-square = 4.000, p < 0.05). The correct use of the screening tool significantly increased the sensitivity and thereby the recognition of movement disorders in IMD patients, though referral to a neurologist remains necessary for phenotype identification.

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.

BACKGROUND:Riboflavin transporter deficiency (RTD) is an inborn error of riboflavin transport causing progressive neurological symptoms if left untreated. While infants with symptomatic RTD rapidly deteriorate, presentation later in childhood or in adulthood is more gradual. Symptoms overlap with more common diseases, carrying a risk of misdiagnosis, and given the relatively recent discovery of the genetic basis of RTD in 2010 it is likely that older patients have not been tested. Treatment with oral riboflavin (vitamin B2) halts disease progression and can be lifesaving. We hypothesized that patients may have been left unrecognized at the time of presentation and therefore we performed a datamining study to detect undiagnosed RTD patients in a tertiary referral hospital. METHODS:A systematic search in Electronic Health Records (EHR) of all patients visiting the Amsterdam University Medical Centers between January 2004 and July 2021 was performed by a medical data text-mining tool. Pseudonymized patient records, matching pre-defined search terms (hearing loss or auditory neuropathy spectrum disorders combined with key clinical symptoms or riboflavin) were screened and included if no definitive alternative diagnosis for symptoms indicating possible RTD was found. Included patients were offered genetic testing. We documented total number of patients with possible RTD, number of patients that underwent genetic testing for RTD and results of genetic testing. RESULTS:EHR of 2.288.901 patients were automatically screened. Thirteen patients with possible RTD were identified and offered genetic testing. Seven patients chose not to participate. Genetic testing was performed in 6 patients and was negative. The datamining did detect all previously known RTD patients in the hospital. CONCLUSIONS:By screening a large cohort of patients of all ages in a tertiary referral hospital in a period spanning 17 years, no new RTD patients were found. Although not all suspected patients underwent genetic testing, our findings suggest that the prevalence of RTD is low and the chance of having missed this diagnosis in a tertiary referral hospital is limited.

Classic galactosemia (CG, OMIM #230400, ORPHA: 79,239) is a hereditary disorder of galactose metabolism that, despite treatment with galactose restriction, affects brain function in 85% of the patients. Problems with cognitive function, neuropsychological/social emotional difficulties, neurological symptoms, and abnormalities in neuroimaging and electrophysiological assessments are frequently reported in this group of patients, with an enormous individual variability. In this review, we describe the role of impaired galactose metabolism on brain dysfunction based on state of the art knowledge. Several proposed disease mechanisms are discussed, as well as the time of damage and potential treatment options. Furthermore, we combine data from longitudinal, cross-sectional and retrospective studies with the observations of specialist teams treating this disease to depict the brain disease course over time. Based on current data and insights, the majority of patients do not exhibit cognitive decline. A subset of patients, often with early onset cerebral and cerebellar volume loss, can nevertheless experience neurological worsening. While a large number of patients with CG suffer from anxiety and depression, the increased complaints about memory loss, anxiety and depression at an older age are likely multifactorial in origin.

Long-term outcomes in classic galactosemia (CG) have been studied previously, but all prior studies have relied on cohorts of patients that were small in number, or heavily skewed toward children and young adults, or both. Here, we extend what is known about the health and well-being of maturing adults with CG by analyzing the results of anonymous custom surveys completed by 92 affected individuals, ages 30-78, and 38 unaffected sibling controls, ages 30-79. The median age for patients was 38.5 years and for controls was 41 years. These study participants hailed from 12 different countries predominantly representing Europe and North America. Participants reported on their general life experiences and outcomes in seven different domains including: speech/voice/language, cognition, motor function, cataracts, bone health, psychosocial well-being, and gastrointestinal health. We also queried women about ovarian function. Our results indicated a prevalence of long-term complications across all outcome domains that aligned with levels previously reported in younger cohorts. Given the sample size and age range of participants in this study, these findings strongly suggest that the adverse developmental outcomes commonly linked to CG are not progressive with age for most patients. We also tested four candidate modifiers for possible association with each of the outcomes followed, including: days of neonatal milk exposure, rigor of dietary galactose restriction in early childhood, current age, and home continent. We observed no associations that reached even nominal significance, except for the following: cataracts with neonatal milk exposure (p = 2.347e-04), cataracts with age (p = 0.018), and bone health with home continent (p = 0.03).

Abstract Classical galactosemia (CG) is an autosomal recessive disorder of galactose metabolism. Despite early initiation of a galactose‐restricted diet, patients develop long‐term complications including cognitive impairment. There is an ongoing debate whether the cognitive impairment in CG is stable throughout life or progresses with age. Earlier cross‐sectional and longitudinal studies regarding intelligence suggest stability, but longitudinal neuropsychological studies focusing on specific cognitive functions are limited. Therefore, the aim of this study is to assess cognitive change over time in adult CG‐patients. Ten adult patients with normal to borderline intelligence (mean age 33 years, range 22–49; IQ≥70 or independent work‐ or living situation) were assessed twice with a mean time interval of 3 years and 9 months (range 1023–1575 days). The neuropsychological assessments covered information processing speed, executive functioning, verbal fluency, and visuospatial functioning. Results showed that there was no significant decline or improvement in test scores on all neuropsychological measures except a decline on the Trail Making Test‐A (p = 0.048). However, this group‐level difference was subject to “regression to the mean” and was not endorsed by significant change in test scores measuring the same cognitive domain. Moreover, no specific pattern of reliable change (RCI > ‐1.96) was present on specific measures or within individual patients. This explorative study performed in 10 adult CG‐patients with normal to borderline intelligence revealed no cognitive change on several cognitive domains. This implies that the subset of adults with a normal to borderline IQ in their early and middle adulthood are cognitively stable.

Inconclusive and false-positive newborn screening (NBS) results can cause parental stress and increase healthcare expenditures. These results can be reduced by improving NBS algorithms. This was recently done for Congenital Hypothyroidism (CH), Congenital Adrenal Hyperplasia (CAH) and Maple Syrup Urine Disease (MSUD) in the Dutch NBS program. The current study estimates the financial consequences of these improved algorithms related to the reduction in inconclusive results and false-positives. For each improved algorithm, the care pathway of an inconclusive/false-positive result was analyzed. The costs associated with the improvements, based on the change in inconclusive results/false-positives, were assessed to estimate the cost reduction per year. The improvements resulted in a reduction of inconclusive results and/or false-positives, without increasing false-negatives. For CH, false positives decreased by 26 per year with a related cost reduction of EUR 31,156. For CAH, 95 second heel punctures and seven false-positives per year were avoided, leading to a related cost reduction of EUR 7340. For MSUD, five false-positives per year were avoided with a related cost reduction of EUR 11,336. The improved screening algorithms led to a cost reduction of EUR 49,832 annually. Together with the known negative psychosocial effects associated with an inconclusive or false-positive NBS result, these results highlight the importance of improving NBS algorithms.

Current management guidelines for urea cycle disorders (UCDs) offer clear strategies, incorporating both authorized and non-authorized medicinal products (including intravenous formulations and products regulated as food). These varying product categories are subject to specific accessibility challenges related to availability, reimbursement, and pricing. The aim of this study is to identify potential obstacles to optimal UCD treatment implementation in European clinical practice. A survey aimed at metabolic healthcare professionals (HCPs) managing patients with UCDs in Europe was disseminated through the European Reference Network for Hereditary Metabolic Disorders and the European registry and network for intoxication type metabolic diseases. Forty-eight survey responses were collected from 21 European countries. In 16 of these countries, at least one metabolic HCP reported challenges in accessing UCD products. Reimbursement issues were reported for most products (8/10), including both authorized and non-authorized products. Availability-related challenges were also reported for 8/10 products, although unavailability was limited to non-authorized products. Prices impacted accessibility for all authorized products (3/3) and one non-authorized IV product. The accessibility of UCD treatment products varied across Europe, although no clear regional variations could be discerned. Survey data revealed that metabolic HCPs experience challenges in accessing both authorized and non-authorized products for UCD management in the majority of European countries. This indicates that registering unauthorized products may not resolve all issues. Improved reimbursement policies and fair pricing models, as well as (adjusted) authorization procedures may help address these concerns, thereby optimizing treatment access for UCD patients.

Patients with classic galactosemia (CG), an inborn error of galactose metabolism, suffer from impairments in cognition, including language processing. Potential causes are atypical brain oscillations. Recent electroencephalogram (EEG) showed differences in the P300 event-related-potential (ERP) and alterations in the alpha/theta-range during speech planning. This study investigated whether transcranial alternating current stimulation (tACS) at theta-frequency compared to sham can cause a normalization of the ERP post stimulation and improves language performance. Eleven CG patients and fourteen healthy controls participated in two tACS-sessions (theta 6.5 Hz/sham). They were engaged in an active language task, describing animated scenes at three moments, that is, pre/during/post stimulation. Pre and post stimulation, behavior (naming accuracy, voice-onset-times; VOT) and mean-amplitudes of ERP were compared, by means of a P300 time-window analysis and cluster-based-permutation testing during speech planning. The results showed that theta stimulation, not sham, significantly reduced naming error-percentage in patients, not in controls. Theta did not systematically speed up naming beyond a general learning effect, which was larger for the patients. The EEG analysis revealed a significant pre-post stimulation effect (P300/late positivity), in patients and during theta stimulation only. In conclusion, theta-tACS improved accuracy in language performance in CG patients compared to controls and altered the P300 and late positive ERP-amplitude, suggesting a lasting effect on neural oscillation and behavior.

Progress in genetic diagnosis and orphan drug legislation has opened doors to new therapies in rare neurogenetic diseases (RNDs). Innovative therapies such as gene therapy can improve patients' quality of life but come with academic, regulatory, and financial challenges. Registries can play a pivotal role in generating evidence to tackle these, but their development requires multidisciplinary knowledge and expertise. This study aims to develop a practical framework for creating and implementing patient registries addressing common challenges and maximizing their impact on care, research, drug development, and regulatory decision making with a focus on RNDs. A comprehensive 3-step literature and qualitative research approach was used to develop the framework. A qualitative systematic literature review was conducted, extracting guidance and practices leading to the draft framework. Subsequently, we interviewed representatives of 5 established international RND registries to add learnings from hands-on experiences to the framework. Expert input on the draft framework was sought in digital multistakeholder focus groups to refine the framework. The literature search; interviews with 5 registries; and focus groups with patient representatives (n = 4), clinicians (n = 6), regulators, health technology assessment (HTA) bodies and payers (n = 7), industry representatives (n = 7), and data/information technology (IT) specialists (n = 5) informed development of the framework. It covers the interests of different stakeholders, purposes for data utilization, data aspects, IT infrastructure, governance, and financing of rare disease registries. Key principles include that data should be rapidly accessible, independent, and trustworthy. Governance should involve multiple stakeholders. In addition, data should be highly descriptive, machine-readable, and accessible through a shared infrastructure and not spread over multiple isolated repositories. Sustainable and independent financing of registries is deemed important but remains challenging because of a lack of widely supported funding models. The proposed framework will guide stakeholders in establishing or improving rare disease registries that fulfill requirements of academics and patients as well as regulators, HTA bodies, and commercial parties. There is a need for more clarity regarding quality requirements for registries in regulatory and HTA context. In addition, independent financing models for registries should be developed, as well as well-defined policies on technical uniformity in health data.

Objective: Classical galactosemia (CG) is an inborn error of galactose metabolism. Many CG patients suffer from long-term complications including poor cognitive functioning. There are indications of social dysfunction but limited evidence in the literature. Therefore, this study aims to improve our understanding of social competence in CG by investigating social cognition, neurocognition and emotion regulation.Methods: A comprehensive (neuro)psychological test battery, including self and proxy questionnaires, was administered to CG patients without intellectual disability. Social cognition was assessed by facial emotion recognition, Theory of Mind and self-reported empathy. Standardised results were compared to normative data of the general population.Results: Data from 23 patients (aged 8-52) were included in the study. On a group level, CG patients reported satisfaction with social roles and no social dysfunction despite the self-report of lower social skills. They showed deficits in all aspects of social cognition on both performance tests (emotion recognition and Theory of Mind) and self-report questionnaires (empathy). Adults had a lower social participation than the general population. Parents reported lower social functioning, less adaptive emotion regulation and communication difficulties in their children. Individual differences in scores were present.Conclusion: This study shows that CG patients without intellectual disability are satisfied with their social competence, especially social functioning. Nevertheless, deficits in social cognition are present in a large proportion of CG patients. Due to the large variability in scores and discrepancies between self- and proxy-report, an individually tailored, comprehensive neuropsychological assessment including social cognition is advised in all CG patients. Treatment plans need to be customised to the individual patient.