Cost-benefit analysis: newborn screening for inborn errors of metabolism in Lebanon

Current Status of Newborn Bloodspot Screening Worldwide 2024: A Comprehensive Review of Recent Activities (2020-2023)

Newborn bloodspot screening (NBS) began in the early 1960s based on the work of Dr. Robert "Bob" Guthrie in Buffalo, NY, USA. His development of a screening test for phenylketonuria on blood absorbed onto a special filter paper and transported to a remote testing laboratory began it all. Expansion of NBS to large numbers of asymptomatic congenital conditions flourishes in many settings while it has not yet been realized in others. The need for NBS as an efficient and effective public health prevention strategy that contributes to lowered morbidity and mortality wherever it is sustained is well known in the medical field but not necessarily by political policy makers. Acknowledging the value of national NBS reports published in 2007, the authors collaborated to create a worldwide NBS update in 2015. In a continuing attempt to review the progress of NBS globally, and to move towards a more harmonized and equitable screening system, we have updated our 2015 report with information available at the beginning of 2024. Reports on sub-Saharan Africa and the Caribbean, missing in 2015, have been included. Tables popular in the previous report have been updated with an eye towards harmonized comparisons. To emphasize areas needing attention globally, we have used regional tables containing similar listings of conditions screened, numbers of screening laboratories, and time at which specimen collection is recommended. Discussions are limited to bloodspot screening.

Screening of 1.17 million newborns for inborn errors of metabolism using tandem mass spectrometry in Shanghai, China: A 19-year report

BACKGROUND

Inborn errors of metabolism (IEMs) frequently result in progressive and irreversible clinical consequences if not be diagnosed or treated timely. The tandem mass spectrometry (MS/MS)-based newborn screening (NBS) facilitates early diagnosis and treatment of IEMs. The aim of this study was to determine the characteristics of IEMs and the successful deployment and application of MS/MS screening over a 19-year time period in Shanghai, China, to inform national NBS policy.

METHODS

The amino acids and acylcarnitines in dried blood spots from 1,176,073 newborns were assessed for IEMs by MS/MS. The diagnosis of IEMs was made through a comprehensive consideration of clinical features, biochemical performance and genetic testing results. The levels of MS/MS testing parameters were compared between various IEM subtypes and genotypes.

RESULTS

A total of 392 newborns were diagnosed with IEMs from January 2003 to June 2022. There were 196 newborns with amino acid disorders (50.00%, 1: 5910), 115 newborns with organic acid disorders (29.59%, 1: 10,139), and 81 newborns with fatty acid oxidation disorders (20.41%; 1:14,701). Phenylalanine hydroxylase deficiency, methylmalonic acidemia and primary carnitine deficiency were the three most common disorders. Some hotspot variations in eight IEM genes (PAH, SLC22A5, MMACHC, MMUT, MAT1A, MCCC2, ACADM, ACAD8), 35 novel variants and some genotype-biochemical phenotype associations were identified.

CONCLUSIONS

A total of 28 types of IEMs were identified, with an overall incidence of 1: 3000 in Shanghai, China. Our study offered clinical guidance for the implementation of MS/MS-based NBS and genetic counseling for IEMs in this city.

A retrospective analysis of MS/MS screening for IEM in high-risk areas

Inborn errors of metabolism (IEM) can lead to severe motor and neurological developmental disorders and even disability and death in children due to untimely treatment. In this study, we used tandem mass spectrometry (MS/MS) for primary screening and recall of those with positive primary screening for rescreening. Further diagnosis was based on biochemical tests, imaging and clinical presentation as well as accurate genetic testing using multi-gene panel with high-throughput sequencing of 130 IEM-related genes. The screening population was 16,207 newborns born between July 1, 2019, and December 31, 2021. Based on the results, 8 newborns were diagnosed with IEM, constituting a detection rate of 1:2,026. Phenylketonuria was the most common form of IEM. In addition, seven genes associated with IEM were detected in these eight patients. All eight patients received standardized treatment starting in the neonatal period, and the follow-up results showed good growth and development. Therefore, our study suggests that MS/MS rescreening for IEM pathogenic variants in high-risk areas, combined with a sequencing validation strategy, can be highly effective in the early detection of affected children. This strategy, combined with early intervention, can be effective in preventing neonatal morbidity and improving population quality.

Does health economics research align with the disease burden in the Middle East and North Africa region? A systematic review of economic evaluation studies on public health interventions

Introduction

Economic evaluation studies demonstrate the value of money in health interventions and enhance the efficiency of the healthcare system. Therefore, this study reviews published economic evaluation studies of public health interventions from 26 Middle East and North Africa (MENA) countries and examines whether they addressed the region's major health problems.

Methods

PubMed and Scopus were utilized to search for relevant articles published up to June 26, 2021. The reviewers independently selected studies, extracted data, and assessed the quality of studies using the Consolidated Health Economic Evaluation Reporting Standards (CHEERS) checklist.

Results

The search identified 61 studies. Approximately half (28 studies; 46%) were conducted in Israel and Iran. The main areas of interest for economic evaluation studies were infectious diseases (21 studies; 34%), cancers (13 studies; 21%), and genetic disorders (nine studies; 15%). Five (8%), 39 (64%), 16 (26%), and one (2%) studies were classified as excellent, high, average, and poor quality, respectively. The mean of CHEERS checklist items reported was 80.8% (SD 14%). Reporting the structure and justification of the selected model was missed in 21 studies (37%), while price and conversion rates and the analytical methods were missed in 21 studies (34%).

Conclusions

The quantity of economic evaluation studies on public health interventions in the MENA region remains low; however, the overall quality is high to excellent. There were obvious geographic gaps across countries regarding the number and quality of studies and gaps within countries concerning disease prioritization. The observed research output, however, did not reflect current and upcoming disease burden and risk factors trends in the MENA region.

Challenges of genetic diagnosis of inborn errors of metabolism in a major tertiary care center in Lebanon

Background: Inborn errors of metabolism are rare genetic disorders; however, these are prevalent in countries with high consanguinity rates, like Lebanon. Patients are suspected, based on a combination of clinical and biochemical features; however, the final confirmation relies on genetic testing. Using next generation sequencing, as a new genetic investigational tool, carries several challenges for the physician, the geneticist, and the families. Methods: In this retrospective study, we analyzed the clinical, biochemical, and genetic profile of inborn errors of metabolism suspected patients, seen at a major tertiary care center in Lebanon, between 2015 and 2018. Genetic testing was performed using next generation sequencing. Genotype-phenotype correlation and diagnostic yield of each testing modality were studied. Results: Out of 211 patients genetically tested, 126 were suspected to have an inborn error of metabolism. The diagnostic yield of next generation sequencing reached 64.3%. Single gene testing was requested in 53%, whole exome sequencing in 36% and gene panels in 10%. Aminoacid disorders were mostly diagnosed followed by storage disorders, organic acidemias and mitochondrial diseases. Targeted testing was performed in 77% of aminoacid and organic acid disorders and half of suspected storage disorders. Single gene sequencing was positive in 75%, whereas whole exome sequencing diagnostic yield for complex cases, like mitochondrial disorders, reached 49%. Good clinical and biochemical correlation allowed the interpretation of variants of unknown significance and negative mutations as well as therapeutic management of most patients. Conclusion: Tailoring the choice of test modality, by next generation sequencing, to the category of suspected inborn errors of metabolism may lead to rapid diagnosis, shortcutting the cost of repeated testing. Whole exome sequencing as a first-tier investigation may be considered mainly for suspected mitochondrial diseases, whereas targeted sequencing can be offered upon suspicion of a specific enzyme deficiency. Timing and modality of gene test remain challenging, in view of the cost incurred by families.

Population-based screening of newborns: Findings from the newborn screening expansion study (part two)

Rapid advances in genomic technologies to screen, diagnose, and treat newborns will significantly increase the number of conditions in newborn screening (NBS). We previously identified four factors that delay and/or complicate NBS expansion: 1) variability in screening panels persists; 2) the short duration of pilots limits information about interventions and health outcomes; 3) recent recommended uniform screening panel (RUSP) additions are expanding the definition of NBS; and 4) the RUSP nomination and evidence review process has capacity constraints. In this paper, we developed a use case for each factor and suggested how model(s) could be used to evaluate changes and improvements. The literature on models was reviewed from a range of disciplines including system sciences, management, artificial intelligence, and machine learning. The results from our analysis highlighted that there is at least one model which could be applied to each of the four factors that has delayed and/or complicate NBS expansion. In conclusion, our paper supports the use of modeling to address the four challenges in the expansion of NBS.

Cost-effectiveness analysis of newborn screening by tandem mass spectrometry in Shenzhen, China: value and affordability of new screening technology

Background

Newborn screening (NBS) can prevent inborn errors of metabolism (IEMs), which may cause long-term disability and even death in newborns. However, in China, tandem mass spectrometry (MS/MS) screening has just started. This study aimed to assess the cost-effectiveness of NBS using MS/MS in Shenzhen under the nationally recommended program, as well as evaluate the value and affordability of introducing this new screening technology.

Methods

A Markov model was built to estimate the cost and quality-adjusted life-years (QALYs) of different screening programs. We compared PKU screening using traditional immunofluorescence (IF) with the other 11 IEMs not screened and all 12 IEMs screened using MS/MS, and the programs detecting different numbers of IEMs chosen from the national recommended program were also compared. A sensitivity analysis and budget impact analysis (BIA) were performed.

Results

The incremental cost-effectiveness ratio (ICER) of detecting all 12 IEMs in the national program is 277,823 RMB per QALY, below three times per capita GDP in Shenzhen. MS/MS screening in Shenzhen can be cost-effective only if at least three diseases (PKU, PCD and MMA) are covered and when the screening program covers five diseases (PKU, PCD, MMA, MSUD, IVA), the ICER closely approaches its critical threshold. The BIA indicated the implementation cost of the national program to be around 490 million RMB over 10 years and showed no difference in budget between programs detecting different numbers of IEMs.

Conclusions

We conclude that the newborn screening using MS/MS in Shenzhen is cost-effective, and the budget affordable for the Shenzhen government. Two concepts for selecting the IEMs to be detected are also presented. One is to choose the most cost-effective screening programs detecting highest number of IEMs to achieve a minimal ICER. The other considers the curability and affordability of the disease as the basis of healthcare decisions to screen suitable IEMs, achieving an ICER under the threshold and close to the minimum value.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12913-022-08394-4.

Prevalence of methylmalonic acidemia among newborns and the clinical-suspected population: a meta-analyse

IMPORTANCE

Knowing the scale of rare inborn errors is important for screening and resource allocation. Evidence on the prevalence of methylmalonic acidemia (MMA) among newborns and the clinical-suspected population from large-scale screening programs needs to be systematically synthesized.

OBJECTIVE

To estimate the worldwide prevalence of MMA for newborns and the clinical-suspected population and explore the differences in different regions, periods, and diagnostic technologies.

DATA SOURCES

MEDLINE, Embase, CRD, Cochrane Library, Scopus, CINAHL, and PROSPERO. Study Selection: All studies reporting the epidemiology characteristics of MMA were selected.

DATA EXTRACTION AND SYNTHESIS

Characteristics of study, subjects, and epidemiology were extracted, random-effect models were used for meta-analyses.

MAIN OUTCOME AND MEASURE

Pooled prevalence of MMA.

RESULTS

This study included 111 studies. The pooled prevalence of MMA worldwide was 1.14 per 100,000 newborns (1516/190,229,777 newborns, 95% CI: 0.99-1.29) and 652.11 per 100,000 clinical-suspected patients (1360/4,805,665 clinical-suspected individuals, CI: 544.14-760.07). Asia and Africa got a higher pooled prevalence of MMA. The prevalence of MMA in newborns increased through the years, while that in the clinical-suspected population decreased. Collecting blood ≥ 72 h after birth had a higher pooled prevalence of MMA than collecting during 24 h-72 h after birth. The combining-use of MS/MS and GC/MS had a higher pooled prevalence than the single-use of MS/MS or GC/MS. Prevalence of cbl C, mut, cbl B, cbl A, isolated MMA, combined MMA and homocystinuria, vitamin B12-responsive MMA was synthesized.

CONCLUSIONS AND RELEVANCE

Prevalence of MMA among newborns was extremely low, but considerably high in the clinical-suspected population, indicating the need for more efficient newborn screening strategies and closer monitoring of the high-risk population for the early signs of MMA. Asia and Africa should attach importance to the high prevalence of MMA. Further diagnostic tests were recommended for the combining-use vs single-use of MS/MS and GC/MS and for collecting blood after 72 h vs during 24-72 h after birth.

Catalogue for Transmission Genetics in Arabs (CTGA) Database: Analysing Lebanese Data on Genetic Disorders

Lebanon has a high annual incidence of birth defects at 63 per 1000 live births, most of which are due to genetic factors. The Catalogue for Transmission Genetics in Arabs (CTGA) database, currently holds data on 642 genetic diseases and 676 related genes, described in Lebanese subjects. A subset of disorders (14/642) has exclusively been described in the Lebanese population, while 24 have only been reported in CTGA and not on OMIM. An analysis of all disorders highlights a preponderance of congenital malformations, deformations and chromosomal abnormalities and demonstrates that 65% of reported disorders follow an autosomal recessive inheritance pattern. In addition, our analysis reveals that at least 58 known genetic disorders were first mapped in Lebanese families. CTGA also hosts 1316 variant records described in Lebanese subjects, 150 of which were not reported on ClinVar or dbSNP. Most variants involved substitutions, followed by deletions, duplications, as well as in-del and insertion variants. This review of genetic data from the CTGA database highlights the need for screening programs, and is, to the best of our knowledge, the most comprehensive report on the status of genetic disorders in Lebanon to date.

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.

Institutional experience of newborn screening for inborn metabolism disorders by tandem MS in the Turkish population

Background The tandem mass spectrometry method in the screening of congenital metabolic disorders is not included in routine national newborn screening programmes in Turkey. To evaluate the distribution of acylcarnitines and amino acid levels in normal newborns, establish acylcarnitine and amino acid cut-off levels and further preliminary results of inherited metabolic disorders inferentially in the Turkish population. Methods Newborn screening tests performed by tandem MS from 2016 to 2018 were retrospectively reviewed. The study group included 17,066 newborns born in our hospitals located in various regions of Turkey. Blood samples were obtained from infants older than 24 h of age. Among the 17,066 newborns, the metabolic screening data of 9,994 full-term newborns (>37 weeks) were employed to obtain the percentile distribution of the normal population. The study group (17,066) was screened for 26 types of inborn error of metabolism. Results Our established cut-offs, were compared with the cut-offs determined by Region for Stork Study and Centers for Disease Control. Among the 26 screened disorders, a total of 12 cases (8 amino acid metabolism disorders, 1 urea cycle defect, 2 organic acidaemias and 1 fatty acid oxidation disorder) were identified. Conclusions Because of the high rate of consanguineous marriages in Turkey, the development of a nationwide screening panel is necessary for early detection and management of potentially treatable inherited metabolic disorders.

Inborn errors of metabolism detectable by tandem mass spectrometry in Beijing

Background Individual inborn errors of metabolism (IEMs) are rare disorders. Expanded newborn screening for IEMs by tandem mass spectrometry (TMS) is an efficient approach for early diagnosis. Here we provide the newborn screening program for the application of this approach (between July 2014 and March 2019) to the identification of newborns in Beijing at risk of developing a potentially fatal disease. Methods The amino acids and acylcarnitines in dried blood spots were analyzed by TMS. Diagnoses of newborns with elevated metabolites were confirmed by gas chromatography-mass spectrometry, biochemical studies, and genetic analysis. Results Among the healthy newborns, 16 metabolic disorder cases were confirmed, giving a total birth prevalence of 1:3666 live births. Organic acidemia (OA) was the most common (9/16 patients; 56%), and methylmalonic acidemia was the most frequently observed OA (7/9 patients; 89%). Five infants were diagnosed with methylmalonic acidemia with homocystinuria type CblC, two with isolated methylmalonic acidemia, one with propionic acidemia, and one with isovaleric acidemia. Four patients (4/16, 25%) were diagnosed with hyperphenylalaninemia. One suffered with medium-chain acyl CoA dehydrogenase deficiency, one with carnitine uptake deficiency, and one with citrin deficiency. Eleven cases underwent genetic analysis. Seventeen mutations in eight IEM-associated genes were identified in 11 confirmed cases. Symptoms were already present within 2 days after birth in 44% (7/16) cases. The infant with propionic acidemia died at 7 days after birth. The other cases received timely diagnosis and treatment, and most of them grew well. Conclusions The results illustrate challenges encountered in disease management highlighting the importance of newborn screening for inherited metabolic disorders, which is not yet nationally available in our country. Regional newborn screening programs will provide a better estimation of the incidence of IEM.

Expanded newborn screening for inborn errors of metabolism by tandem mass spectrometry in newborns from Xinxiang city in China

Background

Tandem mass spectrometry is a powerful technology available in China over the last 15 years. The development of tandem mass spectrometry had made it possible to rapidly screen newborns for inborn errors of metabolism. The aim of this study was to determine the birth incidence of inborn errors of metabolism through expanded screening of newborns by tandem mass spectrometry in Xinxiang area.

Methods

Dried blood spots from 50 112 newborns were assessed for inborn errors of metabolism by tandem mass spectrometry. The diagnoses were confirmed based on the clinical features, conventional laboratory tests, and the organic acid levels tested in urine by gas chromatography‐mass spectrometry.

Results

The study findings revealed that 31 newborns were diagnosed with inborn errors of metabolism. The total incidence rate of inborn errors of metabolism was 1/1617, and these included 16 cases of amino acid disorders (51.6%), nine cases of organic acid disorders (29.0%), and 6 (19.4%) cases of fatty acid beta‐oxidation disorders.

Conclusions

The screening for the incidence of inborn errors of metabolism in Xinxiang area showed that the rate was higher than previously reported. This study provides valuable data which may be useful in facilitating improvements in the expansion of screening to enable early diagnosis and treatment of inborn errors of metabolism before the onset of symptoms.

Inborn Errors of Metabolism in the Era of Untargeted Metabolomics and Lipidomics

Inborn errors of metabolism (IEMs) are a group of inherited diseases with variable incidences. IEMs are caused by disrupting enzyme activities in specific metabolic pathways by genetic mutations, either directly or indirectly by cofactor deficiencies, causing altered levels of compounds associated with these pathways. While IEMs may present with multiple overlapping symptoms and metabolites, early and accurate diagnosis of IEMs is critical for the long-term health of affected subjects. The prevalence of IEMs differs between countries, likely because different IEM classifications and IEM screening methods are used. Currently, newborn screening programs exclusively use targeted metabolic assays that focus on limited panels of compounds for selected IEM diseases. Such targeted approaches face the problem of false negative and false positive diagnoses that could be overcome if metabolic screening adopted analyses of a broader range of analytes. Hence, we here review the prospects of using untargeted metabolomics for IEM screening. Untargeted metabolomics and lipidomics do not rely on predefined target lists and can detect as many metabolites as possible in a sample, allowing to screen for many metabolic pathways simultaneously. Examples are given for nontargeted analyses of IEMs, and prospects and limitations of different metabolomics methods are discussed. We conclude that dedicated studies are needed to compare accuracy and robustness of targeted and untargeted methods with respect to widening the scope of IEM diagnostics.

Age-Specific Cut-off Values of Amino Acids and Acylcarnitines for Diagnosis of Inborn Errors of Metabolism Using Liquid Chromatography Tandem Mass Spectrometry

Liquid Chromatography tandem mass spectrometry (LC-MS/MS) is used for the diagnosis of more than 30 inborn errors of metabolisms (IEMs). Accurate and reliable diagnosis of IEMs by quantifying amino acids (AAs) and acylcarnitines (ACs) using LC-MS/MS systems depend on the establishment of age-specific cut-offs of the analytes. This study aimed to (1) determine the age-specific cut-off values of AAs and ACs in Bangladesh and (2) validate the LC-MS/MS method for diagnosis of the patients with IEMs. A total of 570 enrolled healthy participants were divided into 3 age groups, namely, (1) newborns (1-7 days), (2) 8 days–7 years, and (3) 8–17 years, to establish the age-specific cut-offs for AAs and ACs. Also, 273 suspected patients with IEMs were enrolled to evaluate the reliability of the established cut-off values. Quantitation of AAs and ACs was performed on an automated LC-MS/MS system using dried blood spot (DBS) cards. Then the specimens of the enrolled clinically suspected patients were analyzed by the established method. Nine patients came out as screening positive for different IEMs, including two borderline positive cases of medium-chain acyl-CoA dehydrogenase deficiency (MCAD). A second-tier test for confirmation of the screening positive cases was conducted by urinary metabolic profiling using gas chromatography- mass spectrometry (GC-MS). Out of 9 cases that came out as screening positive by LC-MS/MS, seven cases were confirmed by urinary GC-MS analysis including 3 cases with phenylketonuria, 1 with citrullinemia type II, 1 with methylmalonic acidemia, 1 with isovaleric acidemia and 1 with carnitine uptake defect. Two borderline positive cases with MCAD were found negative by urinary GC-MS analysis. In conclusion, along with establishment of a validated LC-MS/MS method for quantitation of AAs and ACs from the DBS cards, the study also demonstrates the presence of predominantly available IEMs in Bangladesh.

The Prevalence of Phenylketonuria in Arab Countries, Turkey, and Iran: A Systematic Review

Background/Objectives

This paper seeks to identify the prevalence of Phenylketonuria (PKU) in Arab countries, Turkey, and Iran. The study reviewed the existence of comprehensive national newborn screening programs and reported consanguinity rates.

Methods

A computer based literature search was conducted using relevant keywords to retrieve studies conducted on PKU. A total of 34 articles were included. Prevalence was categorized based on the type of screening method used for PKU diagnoses.

Results

The prevalence of classical PKU diagnosed through a comprehensive national newborn screening program ranged from 0.005% to 0.0167%. The highest prevalence was reported in Turkey at 0.0167%, whereas the lowest prevalence was reported in the UAE, 0.005%.

Conclusion

The findings of this review emphasize the need for the establishment of more efficient reporting systems in these countries that would help measure Disability-Adjusted Life Year (DALY) in order to estimate the overall societal burden of PKU.

Aspects of Newborn Screening in Isovaleric Acidemia

Isovaleric acidemia (IVA), an inborn error of leucine catabolism, is caused by mutations in the isovaleryl-CoA dehydrogenase (IVD) gene, resulting in the accumulation of derivatives of isovaleryl-CoA including isovaleryl (C5)-carnitine, the marker metabolite used for newborn screening (NBS). The inclusion of IVA in NBS programs in many countries has broadened knowledge of the variability of the condition, whereas prior to NBS, two distinct clinical phenotypes were known, an "acute neonatal" and a "chronic intermittent" form. An additional biochemically mild and potentially asymptomatic form of IVA and its association with a common missense mutation, c.932C>T (p.A282V), was discovered in subjects identified through NBS. Deficiency of short/branched chain specific acyl-CoA dehydrogenase (2-methylbutyryl-CoA dehydrogenase), a defect of isoleucine degradation whose clinical significance remains unclear, also results in elevated C5-carnitine, and may therefore be detected by NBS for IVA. Treatment strategies for the long-term management of symptomatic IVA comprise the prevention of catabolism, dietary restriction of natural protein or leucine intake, and supplementation with l-carnitine and/or l-glycine. Recommendations on how to counsel and manage individuals with the mild phenotype detected by NBS are required.