Performance metrics after changes in screening protocol for congenital hypothyroidism.

OBJECTIVE To evaluate Michigan newborn screening for congenital hypothyroidism (CH) protocol changes. METHODS This population-based study includes infants born and screened in Michigan (January 1, 1994-June 30, 2010). Screening performance is compared across 4 periods defined by the dried blood spot testing method: (1) thyroxine (T4) with backup thyrotropin, (2) tandem T4 and thyrotropin, (3) primary thyrotropin testing without serial testing, and (4) primary thyrotropin plus serial testing for births weighing <1800 g. Logistic regression is used to test for differences across periods. RESULTS Thyrotropin testing exhibited greater specificity overall and greater likelihood of detection with serial testing relative to primary T4 testing. Tandem T4 and thyrotropin testing appeared more sensitive relative to other protocols, yet it produced significantly more false-positives, and detection may have been affected by overdiagnosis and misclassification. Central CH was no longer detected once T4 testing ceased. CONCLUSIONS Primary thyrotropin plus serial testing for infants at risk for later rising thyrotropin outperformed other newborn screening strategies for classic CH, although 2 false-negatives occurred among normal birth weight infants admitted to the NICU during this testing period. Tandem T4 and thyrotropin screening outperformed other strategies for detection of both classic and central CH combined, although it is associated with increased operating costs. Additional research is necessary to weigh the benefits of increased sensitivity against additional program operating costs.