Microfilter Paper Method for 17α-Hydroxyprogesterone Radioimmunoassay: Its Application for Rapid Screening for Congenital Adrenal Hyperplasia

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Abstract
A new micromethod for measuring a steroid in blood collected on filter paper has been developed. The method is easy and rapid and has the specificity, accuracy and precision of RIA in whole plasma. Less than 20 μl of blood is required, and, therefore, samples may be obtained with heel prick. This method has been applied to the determination of 17α-hydroxyprogesterone (17α-OH-P) for screening patients with congenital adrenal hyperplasia (CAH) due to 21-hydroxylase deficiency. There was excellent correlation (r = .94) between the values of 17α-OH-P obtained by microfilter paper method and those from plasma samples of cord (40 ± 13 ng/ml) and neonatal blood (<3.6 ng/ml) in normal infants. In six neonates at risk for CAH the diagnosis was made utilizing the microfilter paper method. 17α-OH-P concentrations were highly elevated in both filter paper eluates of whole blood (67–360 ng/ml of plasma) and simultaneously obtained plasma concentration (74–395 ng/ml) in affected infants. The concentrations of 17α-OH-P remained unchanged in dried filter paper blood when stored at room temperature for up to 21 days. Thus, filter paper with dried blood may be sent for steroid assay by mail. The ease with which samples may be transported and the minute amount of sample necessary make this method a promising screening test for CAH.