Bloodspot testosterone assay suitable for study of neonates and monitoringof children with congenital adrenal hyperplasia

A bloodspot assay for testosterone has been developed using an antiserum ra ised against testosterone-3-carboxymethyloxime-bovine serum albumin (T-3 CM O-BSA) conjugate and I-125-T-3CMO-histamine tracer. The method has a detect ion limit of 0.4 nmol/L with between-batch precision of less than 15% for t estosterone values between 0.9 and 2.0 nmol/L and less than 10% for values greater than 2.0 nmol/L. Recovery of 4 nmol/L testosterone spiked into whol e blood samples from 16 women (with unspiked bloodspot testosterone concent rations ranging from 0.4 to 3.7 nmol/L) was 100.9%. Bloodspot testosterone concentration was measured in thirty 6-9 day old infants (19 boys, 11 girls ) with an absolute range in boys of < 0.4-2.3 nmol/L and in girls of <0.4 n mol/L. In preterm infants (12 boys, 12 girls) of varying birth gestation an d postnatal age, levels were higher than in term infants, with boys showing a rise with increasing postnatal age. Daytime bloodspot profiles in four c hildren on replacement therapy for congenital adrenal hyperplasia demonstra ted consistently low testosterone levels in the presence of moderately elev ated early morning 17-hydroxyprogesterone concentrations, thus indicating a dequate treatment. The bloodspot testosterone assay can be applied to the s tudy of androgen physiology in preterm neonates as well as for monitoring t reatment in disorders such as congenital adrenal hyperplasia.