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

To evaluate the effectiveness of a second newborn screening for congenital hypothyroidism (CH).

All infants born in Colorado, USA, from July 1996 through June 2004 had a total thyroxine measured with secondary thyroid stimulating hormone determination.

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.

With only one newborn screen for CH, the number of missed cases is significant and higher than previously reported.