Predicting gestational age improves newborn screening for congenital adrenal hyperplasia: a retrospective cohort study

Background: Newborn screening for congenital adrenal hyperplasia (CAH) is increasingly performed using a two-tiered approach; 17-hydroxyprogesterone by immunoassay followed by steroid panel by liquid chromatography mass spectrometry. The first tier uses gestational age (GA)-based 17-hydroxyprogesterone screening thresholds. GA is unreported in approximately 5% of births and, in these cases, birth weight (BW)-based screening thresholds are used. However, BW based thresholds have a lower specificity, resulting in more first tier false positives. combining newborn the screening analytes measured in the blood spot screen, a predictive model this predicted in newborns with an unreported GA. Newborns underwent subsequent GA-based screening to determine whether this method results in a higher positive predictive value (PPV) than current BW-based screening methods. Methods: Screening results were obtained from Newborn Screening Ontario for 702,020 infants that were born in Ontario, Canada between 2011 and 2015. Predicted GA was calculated using a model composed of demographic and screening analyte factors. Newborns with an unreported GA underwent screening using BW and predicted GA, and the PPV for each method was calculated and compared. Descriptive statistics were determined for newborns that screened positive and negative with each algorithm. Results: PPV of first-tier GA-based and BW-based screening and 0.82%, respectively. time PPV of GA-based GA-based PPV of first-tier screening newborns GA Sequential screenings lower false positive true CAH. immune system disorders,