Direct measurement of testosterone in a pediatric center, with use of a radioimmunoassay kit and unextracted serum.

We evaluated a commercial (Radioassay Systems) radioimmunoassay kit for testosterone in which a double-antibody method and an 125I tracer are used. The 50-microL serum sample is assayed directly with no pre-extraction step. The assay system has good sensitivity (0.01 microgram/L), good precision (CV 5.2%), and little cross reactivity between testosterone and other androgens. Results compared well with those by a tritiated radioimmunoassay involving extraction (r = 0.98). Values obtained for 97 children compared well with published pediatric normal values. Evidently, this kit provides a rapid and reliable measurement of testosterone in serum specimens and is acceptable for use with pediatric patients.