Weight-adjusted neonatal 17OH-progesterone cutoff levels improve the efficiency of newborn screening for congenital adrenal hyperplasia.

To evaluate weight-adjusted strategy for levels of neonatal-17OHP in order to improve newborn screening (NBS) efficiency.Blood samples collected between 2-7 days of age from 67,640 newborns were evaluated. When N17OHP levels were ≥ 20 ng/mL, and a second sample was requested. We retrospectively analyzed neonatal-17OHP levels measured by Auto DELFIA- B024-112 assay, grouped according to birth-weight: G1: < 1,500 g, G2: 1,501-2,000 g, G3: 2,000-2,500 g and G4: > 2,500 g. 17OHP cutoff values were determined for each group using the 97.5(th), 99(th), 99.5(th) and 99.8(th) percentiles.0.5% of newborns presented false-positive results using the cutoff level ≥ 20 ng/mL for all groups. Neonates of low birthweight made up 69% of this group. Seven full-term newborns presented congenital adrenal hyperplasia (CAH) and, except for one of them, 17OHP levels were > 120 ng/mL. Only the 99.8(th) percentile presented higher predictive positive value (2%), and lower rate of false-positives in all groups.We suggest the use of 99.8(th) percentile obtained by weight-adjusted N17OHP values of healthy newborns to reduce the rate of false-positive results in NBS.