Evaluating Neonatal Screening Methods for Congenital Hypothyroidism: A Comparative Analysis of Cord Blood and Venous Blood Sampling

Abstract

Early detection of Congenital Hypothyroidism (CH) is crucial to prevent intellectual disability in affected neonates. Neonatal screening for CH typically involves measuring thyroid-stimulating hormone (TSH) and thyroxine (T4) levels, with methods varying between cord blood and venous blood sampling. This study aims to compare the efficacy and reliability of cord blood versus day 3 venous blood sampling in the screening for CH to inform best practices. Methods: This prospective comparative study involved 1,000 term neonates born at Springfield Children’s Hospital over an 18-month period. Cord blood and day 3 venous blood samples were analyzed for T3, T4, and TSH levels using competitive immunoassay techniques. The primary outcomes measured were the mean levels of T3, T4, and TSH, and the secondary outcome was the detection rate of CH based on these hormone levels. Statistical analyses included paired t-tests for continuous variables and sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) calculations for screening efficacy. Results: Significant differences were found in TSH levels between cord blood and day 3 venous samples (p<0.001), but not in T3 and T4 levels. CH was initially suspected in 25 neonates (2.5%) based on cord blood screening and confirmed in 15 neonates (1.5%) on day 3 venous blood screening. The sensitivity and specificity were 100% and 97.5% for cord blood screening, and 100% and 98.5% for day 3 venous blood screening, respectively. PPV and NPV were higher for day 3 venous blood screening compared to cord blood screening. Conclusions: Both cord blood and day 3 venous blood sampling are effective for neonatal CH screening, each with distinct advantages. Day 3 venous sampling, however, demonstrated slightly higher specificity and PPV, suggesting a more accurate reflection of persistent CH. These findings support the use of venous blood sampling on day 3 of life as a reliable method for CH screening, potentially reducing the number of false-positive results and enhancing the early detection and treatment of CH.