Abstract
OBJECTIVE: To analyze the incidence of congenital hypothyroidism (CH) in Putian, optimize the thyroid-stimulating hormone (TSH) screening cut-off value, and improve diagnostic efficiency and accuracy. METHODS: A retrospective analysis was conducted on TSH screening data from 50,539 newborns in Putian between July 2020 and November 2022. TSH concentrations in dried blood spots were measured using time-resolved fluorescence immunoassay (TRFIA). The optimal cut-off value was evaluated using percentile analysis and receiver operating characteristic (ROC) curves. Confirmatory tests included serum TSH, free thyroxine (FT4), and thyroid ultrasound. RESULTS: The detection rate of CH was 1:1,232 (41 cases), with an overall detection rate of 1:555 (including 50 cases of hyperthyrotropinemia). The P99 percentile method determined a TSH cut-off of 11.1 μIU/mL, while ROC curve analysis indicated an optimal cut-off range of 9.33-9.43 μIU/mL (sensitivity 100%, specificity 98.1%, area under the curve [AUC] = 0.997, P < 0.0001). Adopting a revised cut-off of 9.5 μIU/mL reduced recall rates by 10.62% but missed 1 case of hyperthyrotropinemia. Initial TSH positivity exhibited seasonal fluctuations, with higher rates in winter than summer. Among 68 initially negative cases with subsequent elevated venous TSH, 2 were confirmed as CH, highlighting the need for secondary screening in high-risk groups. CONCLUSION: A TSH cut-off of 9.5 μIU/mL optimizes CH screening in Putian, balancing sensitivity (100%) and specificity (98.1%). Seasonal TSH variations and high-risk cases (e.g., preterm infants) highlight the need for tailored protocols. This approach improves screening efficiency and reduces recalls, supporting region-specific adjustments.