MEASUREMENT OF TOTAL SERUM TESTOSTERONE LEVELS USING COMMERCIALLY AVAILABLE KITS - HIGH-DEGREE OF BETWEEN-KIT VARIABILITY

Objective: The measurement of total serum testosterone has an establis hed clinical role in the management of male hypogonadism and female an drogen excess disorders. We studied the between-kit variability and pr ecision of six different commercially available testosterone assays an d compared them with an established in-house method. Design: Laborator y observational prospective study. Setting: Tertiary university medica l center clinical laboratory. Patient(s): Three groups of samples each of men (n = 36) and women (n = 15) who had high, normal, or low level s of sex hormone-binding globulin (SHBG), respectively, were studied. Intervention(s): Individual and pooled (male and female) serum samples were analyzed for total testosterone concentration using six differen t commercially available assays and one in-house method. Main Outcome Measure(s): The between-kit variability and the effect of the mean (+/ - SD) SHBG level were determined, the results obtained with the use of the kits and the in-house method were compared, and the intraassay va riability (i.e., precision) was evaluated. Result(s): Male samples dem onstrated a 26.3%-40.8% variance in the results obtained with differen t kits, which was greatest for samples with the lowest SHBG levels. Fo r female samples, between-kit variability ranged from 57%-115% (averag e, 77%). The percent deviation of the results obtained with the use of commercial methods from those obtained with the use of our in-house a ssay was greater for men (mean variance, 194%) than for women (mean va riance, 67%). The female pool intraassay coefficient of variation was 3.8% with the use of the in-house method and ranged from 8.9%-21.2% wi th the use of the commercial kits. The male pool intraassay coefficien t of variation was 3.1% with the use of the in-house method and ranged from 3.3%-5.5% with the use of the commercial kits. Conclusion(s): Mo st commercially available kits for measuring the total serum testoster one level demonstrated significant between-kit variability, which was greatest for female samples. Further, samples with the lowest SHBG lev els had the highest between-kit variances. These data strongly suggest that the measurement of total serum testosterone using commercial kit s may have limited utility, particularly for the detection of hyperand rogenemia. (C) 1998 by American Society for Reproductive Medicine.