Screen Positivity and Feasibility of Newborn Thyroid Screening Using Postnatal Venous Thyroid-Stimulating Hormone: A Retrospective Cohort Study From Northeast India.

INTRODUCTION: Congenital hypothyroidism (CH) is a preventable cause of intellectual disability when detected and treated early. Postnatal thyroid-stimulating hormone (TSH)-based newborn screening is recommended in India, but evidence from resource-limited settings remains scarce. This study aimed to determine the screen positivity rate and evaluate the feasibility of postnatal venous TSH-based screening. METHODS: This retrospective study included live births at a tertiary care hospital in Northeast India between March 2023 and November 2024 who underwent CH screening using venous TSH estimation at 48-72 hours of life. A TSH value of >20 mIU/L was considered screen-positive according to the Indian Society for Pediatric and Adolescent Endocrinology guidelines. Screen positivity rates were calculated, and associations with clinical variables were explored. Continuous variables were summarized using descriptive statistics, and associations were evaluated using the chi-square test or Fisher's exact test, as appropriate. A p value of <0.05 was considered statistically significant. RESULTS: Of 1,622 live births, 1,132 (69.8%) underwent screening, of whom 1,064 (94.0% of those screened) had analyzable results. Most exclusions resulted from early discharge before sampling and inadequate blood samples. The mean (standard deviation) TSH value was 4.49 (5.19) mIU/L. Nine newborns were screen-positive, yielding a screen positivity rate of 0.85% (8.5 per 1,000 newborns), which decreased to 0.47% after excluding clinically unwell neonates. Among screen-positive newborns, median TSH values were lower in preterm than in term newborns (25.44 vs. 37.52 mIU/L). Maternal thyroid disorder, present in 22.4% of mothers, was not significantly associated with abnormal neonatal TSH (p = 0.73). CONCLUSION: Postnatal venous TSH-based screening was feasible but associated with moderate attrition. The observed screen positivity reinforces the importance of universal newborn screening for CH in this region. Strengthening follow-up and optimizing sample collection, including evaluation of cord blood screening, may enhance the effectiveness of newborn screening programs.