Congenital adrenal hyperplasia and the second newborn screen

Objective: To evaluate the effectiveness of a second newborn screen for congenital adrenal hyperplasia (CAH) in the state of Colorado and report characteristics associated with cases identified on the first versus second screen.

Study design: Colorado implemented newborn screening for CAH with 17-hydroxyprogesterone beginning August 2000. The first screening is performed within 72 hours of life and the second between 8 and 14 days of life. We compared infants diagnosed on the basis of the first versus second newborn screen.

Results: The first screen identified 29 cases of which 28 represented classical CAH. The incidence of classical CAH on the first screen was 1:24,766. The second screen identified 17 additional cases, of which 11 represented classical CAH. Combined, the incidence of classical CAH was 1:17,789. The sensitivity of the first screen was 71.79%. The false negative rate of the first screen was 28.2%. In the absence of a second screen, 1:47,824 infants would have been missed. Infants diagnosed on the first screen had higher 17-hydroxyprogesterone values compared with those diagnosed on the second screen (P = .0008).

Conclusions: The use of a single newborn screen for CAH missed nearly 30% of classical CAH cases in Colorado. Addition of a second screen, therefore, can improve the operating characteristics of the newborn screening program.