Implementing and validating newborn screening for inborn errors of metabolism in South India: a 2-year observational study at a tertiary care hospital.

Introduction: Newborn screening (NBS) is an essential public health initiative for early diagnosis of inborn errors of metabolism (IEM), where timely intervention can reduce morbidity and mortality. While routine in developed countries, NBS is not widely practised in India. This study aimed to implement NBS programme in a tertiary care hospital in South India and validate predetermined cut-off values tailored to the regional population.

Methods: Between 2020 and 2022, 5157 neonates were screened for congenital hypothyroidism (CH), congenital adrenal hyperplasia (CAH), cystic fibrosis (CF), glucose-6-phosphate dehydrogenase (G6PD) deficiency (G6PDD), phenylketonuria (PKU), galactosemia and biotinidase deficiency. Screening was performed using dissociation-enhanced lanthanide fluorescent immunoassay technology on Victor2D platform (Revvity). Markers assessed included 17-α-OH progesterone, neonatal thyroid stimulating hormone, total galactose, immunoreactive trypsinogen, G6PD enzyme, biotinidase enzyme and phenylalanine levels. Data analysis was conducted using R V.4.1.1 software.

Results: Of the 5157 neonates, the recall rates were consistent with those reported in similar studies. However, only 26.7% of screen-positive newborns returned for retesting, indicating a significant gap in awareness about IEMs and the importance of follow-up. Of these, none were diagnosed with CAH; however, four were found to have CH, two had galactosemia, three had G6PDD, one had CF, one had PKU and none had biotinidase deficiency. The confirmed cases were promptly treated and monitored regularly. The distribution of each marker's values fell within 2.5th-97.5th percentiles suggesting consistency.

Conclusion: The reference ranges provided by the manufacturer appear valid in the Indian context. A key challenge identified was low follow-up compliance for screen-positive infants, highlighting the need for enhanced public education on IEM and NBS. Future research will focus on determining the incidence of IEMs and improving parental awareness and follow-up rates.