Utility of a precursor-to-product ratio in the evaluation of presumptive positives in newborn screening of congenital adrenal hyperplasia

TITLE: Utility of a precursor-to-product ratio in the evaluation of presumptive positives in newborn screening of congenital adrenal hyperplasia. OBJECTIVE: Screening for Congenital Adrenal hyperplasia (CAH) caused by 21-α hydroxylase deficiency is challenging because factors such as prematurity and stress increase intermediate steroid metabolite levels in newborn infants. The objective of this study was to explore the use of the 17-OHP/11-deoxycortisol ratio as an adjunct measure in the follow-up evaluation of infants with presumptive positive newborn screens for CAH to distinguish between infants with no disorder and those with CAH. STUDY DESIGN: This was a retrospective cohort study of infants with presumptive positive newborn screens for CAH. The precursor-to-product ratio of 17-OHP/11-deoxycortisol was compared between infants with no disorder (n=47) and infants with CAH (n=5). RESULTS: The CAH infants had higher 17-OHP/11-deoxycortisol ratios than infants with no disorder, 26 (18-58) and 1.05 (0.69-1.46), respectively, p<0.05. Among infants with no disorder, higher levels of serum 17-OHP did not reflect higher ratios, indicating sufficient enzyme activity. CONCLUSIONS: The results suggest that a low 17-OHP/11-deoxycortisol ratio represents 21-α hydroxylase sufficiency among presumptive positives in newborn screening of CAH.