Congenital hypothyroidism and the second newborn metabolic screening in Colorado, USA.

OBJECTIVE: To evaluate the effectiveness of a second newborn screening for congenital hypothyroidism (CH). METHODS: All infants born in Colorado, USA, from July 1996 through June 2004 had a total thyroxine measured with secondary thyroid stimulating hormone determination. RESULTS: The number of first and second newborn screens completed was 494,324 and 471,877, respectively. The first screen identified 185 cases of CH (incidence of 1:2,703). The second screen identified an additional 42 cases. Overall, the incidence based on both the first and second screenings was 1:2,174. The false negative rate for the first screen was 15.6%. In the absence of a second screen, one infant with CH out of every 11,111 babies screened would have been missed. The addition of the second screen increased the cost-per-case identified from dollars 6,108 to dollars 9,730. CONCLUSIONS: With only one newborn screen for CH, the number of missed cases is significant and higher than previously reported.