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Evaluation and long-term follow-up of infants with inborn errors of metabolism identified in an expanded screening
Ma Luz Couce1, Daisy E Castiñeiras, Ma Dolores Bóveda
1Unidad de Diagnóstico y Tratamiento de Enfermedades Metabólicas Congénitas, Departamento de Pediatría, Hospital Clínico Universitario de Santiago, Spain. maria.luz.couce.pico@sergas.es
Insights
Newborn screening in Spain identified 137 inborn errors of metabolism cases over 10 years. Urine sample collection significantly improved detection rates, leading to timely diagnosis and positive outcomes for most infants.
Area of Science:
- Biochemistry
- Genetics
- Pediatrics
Background:
- Newborn screening (NBS) using tandem mass spectrometry was established in Galicia, Spain, in 2000.
- The program initially focused on disorders recommended by the American College of Medical Genetics.
Purpose of the Study:
- To analyze the results of NBS and clinical follow-up for inborn errors of metabolism (IEM) over a 10-year period.
- To evaluate the effectiveness of NBS, including the impact of sample collection timing and type.
Main Methods:
- Analysis of screening and clinical data from 2000 to 2010.
- Inclusion of blood and urine samples collected on the 3rd day of life (since 2002), with earlier samples collected between days 5-8.
- Referral of newborns with abnormal results for diagnosis and treatment.
Main Results:
- 137 IEM cases were identified (1 per 2060 newborns, excluding benign hyperphenylalaninemia).
- Urine samples were crucial, contributing to 44% of IEM detections.
- A high incidence of type I glutaric aciduria (1 in 35,027) was noted. The mortality rate was 2.92%, with 95.5% of survivors asymptomatic.
Conclusions:
- Expanded NBS, particularly with urine sample inclusion, is highly effective in detecting IEM.
- Early detection and treatment lead to favorable clinical outcomes, with most survivors remaining asymptomatic.
- The study provides valuable insights into NBS effectiveness in Spain and highlights the importance of timely sample collection.
Abstract:
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.
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