A Bloodspot Androstenedione Assay Suitable for Home-Monitoring of Steroid Replacement Therapy in Congenital Adrenal Hyperplasia

A bloodspot assay has been developed using an antiserum raised against androstenedione-3-carboxymethyloxime-bovine serum albumin (AD-3CMO-BSA) conjugate and 125I-AD-3CMO-histamine tracer. The method has a detection limit of 0.6 nmol/L blood and a working range from 0.6 to 40 nmol/L blood. The between-batch precision ranged from 8.4% to 23.3%. Bloodspot androstenedione (AD) concentrations were measured in 50 neonates (26 male, 24 female) and in 95 children (54 male, 41 female) aged 6 months to 18 years. No sex difference in concentrations was found in neonates, in pre-pubertal children up to 8 years of age, in pubertal children (males 8-16 years, females 8-14 years) or post-puberty. Bloodspot AD concentrations ranged from less than 0.6 to 2.7 nmol/L in neonates, less than 0.6 nmol/L in pre-pubertal children, 0.6-2.1 nmol/L in pubertal children and less than 0.6-4.6 nmol/L post-puberty. Daytime bloodspot profiles in 10 children on replacement therapy for congenital adrenal hyperplasia generally showed good correlation between 17 alpha-hydroxyprogesterone and AD concentrations (r = 0.928, P less than 0.001). Bloodspot AD profiles have advantages over 17 alpha-hydroxyprogesterone profiles for the assessment of the adequacy of glucocorticoid replacement therapy.