Newborn screening sometimes misses CAH

Negative results on newborn screening do not rule out classic congenital adrenal hyperplasia (CAH) and can delay the diagnosis, according to a new report. The study showed that over a 12-year period, 22% of babies diagnosed with CAH were not identified by newborn screening.

Congenital adrenal hyperplasia is an adrenal gland disorder that appears in 1 in 10,000 to 18,000 children. Newborn infants are screened for CAH to avoid a life-threatening crisis in those with the classic salt-wasting (SW) or simple-virilizing (SV) form of the disease. The rate of false-negatives on screening is not known, however.

From January 1999 through December 2010, 838,241 newborns in Minnesota were screened for CAH. Samples were collected 24 to 48 hours after birth and analyzed for 17α-hydroxyprogesterone level by time-resolved fluoroimmunoassay. Cases of CAH missed by newborn screening were identified by review of the state newborn screening registry and medical records of 3 large pediatric endocrinology centers.

Among the newborns, screening identified 52 children with classic CAH and missed 15 (false-positive rate, 22%). Three of the 9 females missed on screening had ambiguous genitalia but were not diagnosed until aged 3 months, 3.4 years, and 6.5 years. The 6 males missed on screening had significant bone age advancement (median 7 years difference between bone age and chronologic age) but were not diagnosed until aged 2.3 to 5.5 years.

Because newborn screening procedures are similar in most states, false-negative results for CAH may be underestimated, the researchers suggest. They recommend that clinicians be educated about false-negative results to ensure that any patient exhibiting cause for clinical concern about CAH, especially a newborn girl with ambiguous genitalia, receives immediate diagnostic testing.

Go back to the current issue of the eConsult.