A newborn Screening Programme for Inborn errors of metabolism in Galicia: 22 years of evaluation and follow-up.

BACKGROUND: There is a notable lack of harmonisation in newborn screening (NBS) programmes worldwide. The Galician programme for early detection of inborn errors of metabolism (IEM) was one of the first NBS programmes in Europe to incorporate mass spectrometry (July 2000). This programme currently screens for 26 IEMs in dried blood and urine samples collected 24-72 h after birth. RESULTS: In its 22-year history, this programme has analysed samples from 440,723 neonates and identified 326 cases of IEM with a prevalence of 1:1351. The most prevalent IEMs were hyperphenylalaninaemia (n = 118), followed by medium chain acyl-CoA dehydrogenase deficiency (MCADD, n = 26), galactosaemia (n = 20), and cystinurias (n = 43). Sixty-one false positives and 18 conditions related to maternal pathologies were detected. Urine samples have been identified as a useful secondary sample to reduce the rate of false positives and identify new defects. There were 5 false negatives. The overall positive value was 84.23%. The fatality rate over a median of 12.1 years of follow-up was 2.76%. The intelligence quotient of patients was normal in 95.7% of cases, and school performance was largely optimal, with pedagogic special needs assistance required in < 10% of cases. Clinical onset of disease preceded diagnosis in 4% of cases. The age at which first NBS report is performed was reduced by 4 days since 2021. CONCLUSIONS: This study highlights the benefits of collecting urine samples, reduce NBS reporting time and expanding the number of IEMs included in NBS programmes.

Reference values of amino acids, acylcarnitines and succinylacetone by tandem mass spectrometry for use in newborn screening in southwest Colombia.

INTRODUCTION: Inborn errors of metabolism (IEM) represent an important public health problem due to current diagnosis and treatment limitations, poor life quality of affected patients, and consequent untimely child death. In contrast to classical methods, tandem mass spectrometry (MS/MS) has allowed simultaneous evaluation of multiple metabolites associated with IEM offering higher sensitivity, low false positive rates and high throughput. AIMS: Determine concentration levels for amino acids and acylcarnitines in blood of newborns from Colombia, to establish reference values for further use in diagnosis of IEM. METHODS: Implementation of a method to determine amino acids, acylcarnitines and succinylacetone in newborn dried blood spots using MS/MS, and its application in a cross-sectional study conducted in 891 healthy neonates from Cali and Quibdo cities is described. RESULTS: fifty-seven analytes that allow the diagnosis of more than 40 different pathologies were tested. The method showed to be linear, precise and accurate. Healthy neonates 1-18 days of age were included, 523 from Cali and 368 from Quibdo; 52% male and 48% female. Age-related differences on the concentration levels of amino acids and acylcarnitines were observed whereas no significant differences by gender were found. CONCLUSION: The study has contributed to reveal the usual concentration levels of amino acids, acylcarnitines and succinylacetone that could be used as reference for the establishment of a newborn metabolic screening program in Colombia.

INTRODUCCIÓN: Los Errores Innatos del metabolismo (EIM) representan un importante problema de salud pública debido a limitaciones en el tratamiento y diagnóstico oportuno, la pobre calidad de vida de los pacientes afectados, así como la muerte infantil prematura. Comparada con los métodos clásicos, la espectrometría de masas en tándem (MS/MS) ha permitido la evaluación simultánea de múltiples metabolitos asociados con EIM, con una alta sensibilidad, baja proporción de falsos positivos y alto rendimiento. OBJETIVOS: Determinar los niveles de concentración de aminoácidos y acilcarnitinas en sangre de recién nacidos de Colombia, para establecer los valores normales para usarlos como referencia en el diagnóstico de EIM. MÉTODOS: Aquí, se describe la implementación de un método para determinar aminoácidos, acilcarnitinas y succinilacetona en gotas de sangre seca de recién nacidos usando MS/MS, y su aplicación en un estudio de corte transversal realizado en 891 neonatos sanos de las ciudades de Cali y Quibdó. RESULTADOS: Se evaluaron 57 analitos que permiten el diagnóstico de más de 40 patologías diferentes. El método mostró ser lineal, preciso y exacto. Se incluyeron neonatos sanos de 1-18 días de edad, 523 de Cali y 368 de Quibdó, 52% hombres y 48% mujeres. Se observaron diferencias en los niveles de concentración de aminoácidos y acilcarnitinas relacionadas con la edad, mientras que no se encontraron diferencias significativas por sexo. CONCLUSIÓN: El estudio ha contribuido a revelar los niveles usuales de concentración de aminoácidos, acilcarnitinas y succinilacetona que pueden ser usados como referencia para el establecimiento del programa de tamizaje neonatal metabólico en Colombia.

Reference values of amino acids, acylcarnitines and succinylacetone by tandem mass spectrometry for use in newborn screening in southwest Colombia / Valores de referencia de aminoácidos, acilcarnitinas y succinilacetona por espectrometría de masas en tándem para su uso en el tamizaje neonatal en el suroccidente de Colombia

Abstract Introduction: Inborn errors of metabolism (IEM) represent an important public health problem due to current diagnosis and treatment limitations, poor life quality of affected patients, and consequent untimely child death. In contrast to classical methods, tandem mass spectrometry (MS/MS) has allowed simultaneous evaluation of multiple metabolites associated with IEM offering higher sensitivity, low false positive rates and high throughput. Aims: Determine concentration levels for amino acids and acylcarnitines in blood of newborns from Colombia, to establish reference values for further use in diagnosis of IEM. Methods: Implementation of a method to determine amino acids, acylcarnitines and succinylacetone in newborn dried blood spots using MS/MS, and its application in a cross-sectional study conducted in 891 healthy neonates from Cali and Quibdo cities is described. Results: fifty-seven analytes that allow the diagnosis of more than 40 different pathologies were tested. The method showed to be linear, precise and accurate. Healthy neonates 1-18 days of age were included, 523 from Cali and 368 from Quibdo; 52% male and 48% female. Age-related differences on the concentration levels of amino acids and acylcarnitines were observed whereas no significant differences by gender were found. Conclusion: The study has contributed to reveal the usual concentration levels of amino acids, acylcarnitines and succinylacetone that could be used as reference for the establishment of a newborn metabolic screening program in Colombia.

Resumen Introducción: Los Errores Innatos del metabolismo (EIM) representan un importante problema de salud pública debido a limitaciones en el tratamiento y diagnóstico oportuno, la pobre calidad de vida de los pacientes afectados, así como la muerte infantil prematura. Comparada con los métodos clásicos, la espectrometría de masas en tándem (MS/MS) ha permitido la evaluación simultánea de múltiples metabolitos asociados con EIM, con una alta sensibilidad, baja proporción de falsos positivos y alto rendimiento. Objetivos: Determinar los niveles de concentración de aminoácidos y acilcarnitinas en sangre de recién nacidos de Colombia, para establecer los valores normales para usarlos como referencia en el diagnóstico de EIM. Métodos: Aquí, se describe la implementación de un método para determinar aminoácidos, acilcarnitinas y succinilacetona en gotas de sangre seca de recién nacidos usando MS/MS, y su aplicación en un estudio de corte transversal realizado en 891 neonatos sanos de las ciudades de Cali y Quibdó. Resultados: Se evaluaron 57 analitos que permiten el diagnóstico de más de 40 patologías diferentes. El método mostró ser lineal, preciso y exacto. Se incluyeron neonatos sanos de 1-18 días de edad, 523 de Cali y 368 de Quibdó, 52% hombres y 48% mujeres. Se observaron diferencias en los niveles de concentración de aminoácidos y acilcarnitinas relacionadas con la edad, mientras que no se encontraron diferencias significativas por sexo. Conclusión: El estudio ha contribuido a revelar los niveles usuales de concentración de aminoácidos, acilcarnitinas y succinilacetona que pueden ser usados como referencia para el establecimiento del programa de tamizaje neonatal metabólico en Colombia.

The early detection of Salla disease through second-tier tests in newborn screening: how to face incidental findings.

We describe here a 34 months child, practically asymptomatic which presented with high levels of free sialic acid in urine by biochemical detection in second-tier tests newborn screening and with two disease causing mutations in SLC17A5 gene. SLC17A5 mutation analysis showed p.Tyr306* previously described and the novel mutation p.Leu167Pro. This early onset diagnosis allowed us to perform a fast and accurate genetic counseling to the family, helped to better understanding the natural history of this rare disease and probably it could promote cost reduction in future diagnostic tests in the hypothetic case of starting symptoms without diagnosis established. Moreover, an early diagnosis could save family from a long period of time until achieving a definitive diagnostic and to develop an early symptomatic and supportive management of patient to attenuate, as much as possible, disease complications. But, above all, this case illustrates the huge ethical dilemma which arises from any secondary finding (second tier) in newborn screening.

Clinical and metabolic findings in patients with methionine adenosyltransferase I/III deficiency detected by newborn screening.

Persistent hypermethioninemia due to mutations in the MAT1A gene is often found during newborn screening (NBS) for homocystinuria due to cystathionine beta-synthase deficiency, however, outcomes and optimal management for these patients are not well established. We carried out a multicenter study of MAT I/III-deficient patients detected by NBS in four of the Spanish regional NBS programs. Data evaluated during NBS and follow-up for 18 patients included methionine and total homocysteine levels, clinical presentation parameters, genotypes, and development quotients. The birth prevalence was 1:1:22,874. At detection 16 of the 18 patients exhibited elevations of plasma methionine above 60 µmol/L (mean 99.9 ± 38 µmol/L) and the mean value in confirmation tests was 301 µmol/L (91-899) µmol/L. All patients were asymptomatic. In four patients with more markedly elevated plasma methionines (>450 µmol/L) total homocysteine values were slightly elevated (about 20 µmol/L). The average follow-up period was 3 years 7 months (range: 2-123 months). Most patients (83%) were heterozygous for the autosomal dominant Arg264His mutation and, with one exception, presented relatively low circulating methionine concentrations (<400 µM). Additional mutations identified in patients with mean confirmatory plasma methionines above 400 µM were Arg199Cys, Leu355Arg, and a novel mutation, Thr288Ala. During continued follow-up, the patients have been asymptomatic, and, to date, no therapeutic interventions have been utilized. Therefore, the currently available evidence shows that hypermethioninemia due to heterozygous MAT1A mutations such as Arg264His is a mild condition for which no treatment is necessary.

Newborn screening for medium-chain acyl-CoA dehydrogenase deficiency: regional experience and high incidence of carnitine deficiency.

BACKGROUND: Medium-chain acyl-CoA dehydrogenase deficiency (MCADD) is the most common inherited defect in the mitochondrial fatty acid oxidation pathway, resulting in significant morbidity and mortality in undiagnosed patients.Newborn screening (NBS) has considerably improved MCADD outcome, but the risk of complication remains in some patients. The aim of this study was to evaluate the relationship between genotype, biochemical parameters and clinical data at diagnosis and during follow-up, in order to optimize monitoring of these patients. METHODS: We carried out a multicenter study in southwest Europe, of MCADD patients detected by NBS. Evaluated NBS data included free carnitine (C0) and the acylcarnitines C8, C10, C10:1 together with C8/C2 and C8/C10 ratios, clinical presentation parameters and genotype, in 45 patients. Follow-up data included C0 levels, duration of carnitine supplementation and occurrence of metabolic crises. RESULTS: C8/C2 ratio and C8 were the most accurate biomarkers of MCADD in NBS. We found a high number of patients homozygous for the prevalent c.985A > G mutation (75%). Moreover, in these patients C8, C8/C10 and C8/C2 were higher than in patients with other genotypes, while median value of C0 was significantly lower (23 µmol/L vs 36 µmol/L).The average follow-up period was 43 months. To keep carnitine levels within the normal range, carnitine supplementation was required in 82% of patients, and for a longer period in patients homozygotes for the c.985A>G mutation than in patients with other genotypes (average 31 vs 18 months). Even with treatment, median C0 levels remained lower in homozygous patients than in those with other genotypes (14 µmol/L vs 22 µmol/L).Two patients died and another three suffered a metabolic crisis, all of whom were homozygous for the c.985 A>G mutation. CONCLUSIONS: Our data show a direct association between homozygosity for c.985A>G and lower carnitine values at diagnosis, and a higher dose of carnitine supplementation for maintenance within the normal range. This study contributes to a better understanding of the relationship between genotype and phenotype in newborn patients with MCADD detected through screening which could be useful in improving follow-up strategies and clinical outcome.

Glutaric aciduria type I: outcome of patients with early- versus late-diagnosis.

Patients with Glutaric aciduria type 1 (GA-1) can be identified by newborn screening using tandem mass spectrometry. The clinical evolution of screened patients seems to be more favourable compared with those diagnosed later, although long-term evolution is still doubtful. We have evaluated the outcome in nine GA-1 patients diagnosed in our region during 12 years. Six were detected by newborn screening and 3 clinically. The birth prevalence was 1:35,027. High blood C5DC concentration, in 8/9 patients, was found, whereas all patients exhibited high concentration of this metabolite in urine. Therefore, urine C5DC was a good marker for the detection of this disease. Eight different mutations in the GCDH gene were identified, four of them were novel (p.R88H, p.Y398C, p.R372K, p.D220N); being p.R227P the mostcommon. Macrocephaly with enlarged frontotemporal subarachnoid space was present in 4/6 patients diagnosed by newborn screening, all these patients required high energy intake, and in two cases, enteral feeding during the first year of life was needed. One child had an intercurrent episode of feeding refuse with hypoglycemia at two years of age. The mean follow-up time of screened patients was 56 months, and patients still remain asymptomatic. However, after a mean follow-up of 97 months treatment efficacy was poor in unscreened patients, two of them showing a severe spastic tetraparesis. Plasma levels of lysine, tryptophan and carnitine, were the most useful biomarkers for the follow-up. Our data support that, early diagnosis and treatment strategies are essential measures for the good clinical evolution of GA-1 patients.

Development of electrospray ionization tandem mass spectrometry methods for the study of a high number of urine markers of inborn errors of metabolism.

RATIONALE: Rapid and specific screening methods to detect abnormal metabolites in biological fluids are important for the diagnosis of many Inborn Errors of Metabolism (IEM). In Galicia (N.W. Spain), where newborn screening (NBS) has long used both blood and urine dried samples, an expanded NBS by tandem mass spectrometry (MS/MS) begun in July 2000 analyzing amino acids and acylcarnitines in blood. The purpose of this study is the development of methods to widen and to complement the present NBS with the study of the selected metabolites in urine. METHODS: We studied and optimized the fragmentation of a total of 96 marking compounds of IEM, as well as 34 isotopically labeled internal standards (IS). The isobaric interferences were resolved with the use of alternative fragmentation in 14 of the 28 groups found. The methods were validated for 68 compounds following the recommendations of the NCCLS. RESULTS: We have developed electrospray ionization (ESI)- MS/MS methods in positive and negative ionization modes to detect selected metabolites in urine. The study was performed by direct injection of amino acids and acylcarnitines in positive mode, and organic acids, acylglycines, purines and pyrimidines in negative mode. Run times were 2.5 and 2.6 min, respectively, allowing the daily analysis of a high number of samples. CONCLUSIONS: The validated methods were proved effective for the simultaneous study of a large number of metabolites which are commonly present in urine samples and are used for detecting IEM. The evaluation was done by searching diagnostic profiles with multiple markers to increase sensitivity and specificity (e.g., acylcarnitines plus amino acids) or with specific urine markers (cystine, homogentisic acid, sialic acid, N-acetylaspartic acid, etc.).

Evaluation and long-term follow-up of infants with inborn errors of metabolism identified in an expanded screening programme.

Newborn screening (NBS) by tandem mass spectrometry started in Galicia (Spain) in 2000. We analyse the results of screening and clinical follow-up of inborn errors of metabolism (IEM) detected during 10 years. Our programme basically includes the disorders recommended by the American College of Medical Genetics. Since 2002, blood and urine samples have been collected from every newborn on the 3rd day of life; before then, samples were collected between the 5th and 8th days. Newborns who show abnormal results are referred to the clinical unit for diagnosis and treatment. In these 10 years, NBS has led directly to the identification of 137 IEM cases (one per 2060 newborns, if 35 cases of benign hyperphenylalaninemia are excluded). In addition, 33 false positive results and 10 cases of transitory elevation of biomarkers were identified (making the positive predictive rate 76.11%), and 4 false negative results. The use of urine samples contributed significantly to IEM detection in 44% of cases. Clinical symptoms appeared before positive screening results in nine patients (6.6%), four of them screened between days 5 and 8. The death rate was 2.92%; of the survivors, 95.5% were asymptomatic after a mean observation period of 54 months, and only two had an intellectual/psychomotor development score less than 85. Compared to other studies, a high incidence of type I glutaric aciduria was detected, one in 35,027 newborns. This report highlights the benefits of urine sample collection during screening, and it is the first study on expanded newborn screening results in Spain.