Neonatal 17-hydroxyprogesterone levels adjusted according to age at sample collection and birthweight improve the efficacy of congenital adrenal hyperplasia newborn screening

Abstract

IntroductionThe primary concern related to congenital adrenal hyperplasia (CAH) newborn screening (NBS) is the high rate of false-positive results (FPR) associated with prematurity; false-negative results (FNR) can also occur due to precocious sample collection. ObjectiveTo determine the neonatal 17-hydroxyprogesterone (N17OHP) normal range in newborns in Sao Paulo using different references according to age and birthweight (BW) and to establish the optimal NBS cut-off levels. MethodsNeonatal 17-hydroxyprogesterone levels from 271 810 newborns (NBs) according to sample collection time (G1: 48-<72 h and G2: 72 h) and BW (1500 g, 1501-2000 g, 2001-2500 and >2500 g) were evaluated. N17OHP was measured by an fluoroimmunoassay, and serum 17OHP was measured by liquid chromatography-mass spectrometry. Affected and asymptomatic NBs with persistently increased 17OHP levels were submitted to CYP21A2-sequencing. ResultsNeonatal 17-hydroxyprogesterone levels in G1 were lower than G2 in all BW groups (P < 0001). The FPR rate in G1/G2 was 02% using the 998th and 05% using the 995th percentile. The 998th percentile N17OHP value was the best cut-off for distinguishing between unaffected and affected NBs. Forty-four salt wasters, and five simple virilisers were diagnosed; N17OHP levels ranged from 933 to 22098 nmol/l, and no affected neonates with FNR were identified. The positive predictive value in G1 and G2 using the 998th percentile was 56% and 141%, respectively, and 23% and 7%, respectively, using the 995th percentile. Molecular tests identified two NBs with the nonclassical form among the 29 FPR. ConclusionNeonatal 17-hydroxyprogesterone levels adjusted to sample collection age and birthweight reduced the FPR, and the use of N17OHP values based upon the 998th percentile improved the NBS efficacy.