SCREENING FOR CONGENITAL ADRENAL-HYPERPLASIA - THE DELFIA SCREENING-TEST OVERESTIMATES SERUM 17-HYDROXYPROGESTERONE IN PRETERM INFANTS

Objective. To compare 17-hydroxyprogesterone (17-OHP) levels measured by quantitative serum radioimmunoassay (RIA), including an extraction step, and by screening fluoroimmunoassay (FIA) on blood spots in prete rm infants. Methods. Subjects were 39 healthy infants born at less tha n 31 weeks' gestational age. Each infant had weekly blood sampling, an d RIA and FIA were performed on each sample. Results. Two hundred twen ty-seven samples were taken at 28 to 41 weeks' postconceptional age. M ean +/- SD 17-OHP measured by RIA was 11.4 +/- 11.1 nmol/L (0.4 +/- 0. 4 mu g/dL), and decreased over time. Mean +/- SD 17-OHP measured by FI A was 38.96 +/- 37.3 nmol/L, greater than 17-OHP (RIA). Log(Delta FIA- RIA) was inversely related to postconceptional age (R(2) = .39). Concl usion. Screening FIA of blood spots overestimates levels of 17-OHP in preterm infants and should not be used to determine the likelihood of congenital adrenal hyperplasia in this population. We have abandoned F IA screening for congenital adrenal hyperplasia in infants weiging les s than 1500 g.