Newborn screening for congenital hypothyroidism in France: a study of current professional practices

Objective Congenital hypothyroidism is a leading cause of preventable intellectual disability. Neonatal screening enables early detection and treatment, ideally before symptoms appear. In France, screening has been part of national public health policy since 1978, relying on standardized protocols to ensure equity of care. However, the actual adherence to these guidelines and potential local adaptations remain undocumented. This study aimed to describe current practices of French Regional Neonatal Screening Centers and assess their conformity with national recommendations.

Methods In 2024, a cross-sectional descriptive survey was conducted via a structured online questionnaire sent to all 16 French Regional Neonatal Screening Centers. The questionnaire addressed TSH retesting and referral thresholds, use of thyroxine assays, second-tier testing, resampling protocols, and management of preterm infants. Data were analyzed to identify deviations from guidelines and their potential implications.

Results All 16 centers responded (100% response rate). Nine (56%) reported deviations from national recommendations. Five centers applied alternative TSH retesting or referral thresholds. Four measured thyroxine on the first dried blood spot for intermediate TSH levels, with one retrospectively evaluating this approach. Three centers had specific resampling protocols for preterm infants, but none used gestational age-adjusted TSH thresholds. These adaptations aimed to reduce false positives and false negatives associated with the standard protocol.

Conclusions This nationwide survey highlights substantial heterogeneity in congenital hypothyroidism screening practices across France. Variations in TSH thresholds, thyroxine measurement, and preterm infant management may impact diagnostic consistency and equity. Harmonization efforts based on evidence are needed to optimize neonatal screening performance nationally.