Establishing 17-Hydroxyprogesterone Cutoff Values for Congenital Adrenal Hyperplasia in Preterm, Low Birth Weight, and Sick Newborns.

Background: Newborn screening for congenital adrenal hyperplasia (CAH) has benefits with a high adoption rate worldwide. It also has problems of high false positives, which can cause stress to the patient's family with economic losses and unnecessary visits of newborns to hospitals. Therefore, we investigated the influence of birth weight (BW), gestational age (GA), and GA with sampling time on 17-hydroxyprogesterone (17-OHP) concentration and attempted to establish the 17-OHP cutoff values in preterm, low birth weight (LBW), and sick newborns.

Methods: Newborns (n=1,071) born between October 2020 and January 2022 were screened for CAH. Samples from neonates were collected on filter paper with the heel prick method. 17-OHP concentration was measured by time-resolved immunofluorescence with an AutoDELFIA Neonatal 17-hydroxyprogesteron kit and grouped in relation to BW, GA, and GA with sampling time.

Results: The median age of newborns at neonatal sample collection was 6 days. 17-OHP concentration showed a statistically significant negative correlation with BW (r=-0.488, p<0.001) and GA (r=-0.560, p<0.001). Full-term and preterm subgroups had a similar decreasing tendency of 17-OHP concentration with increasing sampling time. Application of newly establishing cutoff criteria significantly reduced recall rates to 1.16%, 0.9%, and 1.75% according to each criterion of BW, GA, and GA with sampling time, respectively.

Conclusions: This study presents new 17-OHP cutoff values for preterm, LBW, and sick newborns. These data in our laboratory can be used as a reference by other laboratories for establishing new cutoff criteria to help lower the high recall rate and reduce unnecessary follow-up tests.