Performance characteristics of a novel tandem mass spectrometry assay for serum testosterone.

BACKGROUND Commercial immunoassays for testosterone (Te) may give inaccurate results for samples from women and children, leading to misdiagnosis and inappropriate treatment. We developed a sensitive and specific tandem mass spectrometric assay for measurement of Te at the concentrations encountered in women and children. METHODS Te was extracted with methyl tert-butyl ether from 100 microL of serum or plasma, derivatized to form an oxime, and reextracted by solid-phase extraction. Instrumental analysis was performed on an API 4000 HPLC tandem mass spectrometer in the multiple-reaction monitoring (MRM) mode. The MRM transitions (m/z) were 304-->124 and 304-->112 for Te and 307-->124 and 307-->112 for d3-Te. RESULTS Within- and between-run CVs were <12% and 7.9%, respectively. The limit of quantification was 0.0346 nmol/L (1 ng/dL). Reference intervals for sex hormone-binding globulin and total, free, and bioavailable Te were established for children of Tanner stages 1 through 5 and adult males and females. CONCLUSIONS The sensitivity and specificity of the method are adequate for analysis of Te in samples from women and children. The method requires small sample volumes, has adequate precision, and is not subject to interferences.