21-Deoxycortisol is a Key Screening Marker for 21-Hydroxylase Deficiency.

OBJECTIVES:To assess whether 21-deoxycortisol (21deoxy) can be used to predict 21-hydroxylase deficiency (21OHD) in newborns and to evaluate the influence of gestational age and the timing of collection on 21deoxy concentrations. STUDY DESIGN:17-hydroxyprogesterone (17OHP) and 21deoxy levels were measured in 906 newborn screening specimens (851 unaffected newborns, 55 confirmed cases of 21OHD) to compare their ability to identify babies with 21OHD. In addition, these 2 steroids were assessed in the unaffected cohort to determine the influence of gestational age (ranging from 23 to 42 weeks) and the timing of specimen collection on the measured concentrations. RESULTS:The gestational age of the newborn impacted both 17OHP and 21deoxy concentrations, but the degree of influence was more substantial for 17OHP. Timing of collection did not affect 21deoxy concentration. Moreover, 21deoxy was a better predictor of 21OHD status compared with 17OHP, with little overlap in concentrations between the unaffected population and confirmed cases of 21OHD. A streamlined decision tree using solely 21deoxy (cutoff value, 0.85 ng/mL) yielded a 91.7% positive predictive value for 21OHD screening. CONCLUSIONS:Our findings demonstrate that 21deoxy is a key disease marker of 21OHD and can be used to improve the accuracy of newborn screening for this disorder.