Radioimmunoassay of Blood-Spot 17α-Hydroxyprogesterone in the Management of Congenital Adrenal Hyperplasia

Abstract

A robust assay for routine measurement of blood-spot 17α-hydroxyprogesterone (17-OHP) concentrations has been developed using a magnetisable, solid-phase antiserum and an 125I-radioligand. The working range of this assay (13.5–500 nmol/L) is well suited for the initial diagnosis of congenital adrenal hyperplasia (CAH) and for monitoring replacement therapy in CAH patients. Data derived from multiple blood-spot samples, collected on two consecutive days, provide 17-OHP profiles. These profiles have been used to construct a chart allowing a rapid visual assessment of the efficacy of replacement therapy in CAH patients. Measurement of 17-OHP in the blood-spots of over-treated patients and accurate determination of normal range values in healthy infants relied on development of a sensitive assay (range 1.7–34 nmol/L). In the blood-spots of normal male ( n=50) and female ( n=50) infants collected 5–7 days after birth, 17-OHP concentrations were 7.62±2.55 nmol/L and 7.32±2.87 nmol/L respectively. Retrospective measurement of this steroid in samples from known CAH patients ( n=4), which had values ranging from 224 to 2145 nmol/L, support a role for measurement of blood-spot 17-OHP in high-risk screening programmes.