RELIABILITY AND VALIDITY OF SERUM SEX-HORMONE MEASUREMENTS

The laboratory reliability and validity of sex hormone measurements we re examined at multiple levels, including lower levels characteristic of children and postmenopausal women. Serum was drawn from four adult male and four adult female healthy volunteers, From each individual's serum pool, a medium- and a low-dilution pool were created. Biochemica l analyses for total and non-sex hormone-binding globulin (SHBG)bound estradiol, estrone, estrone sulfate, progesterone, and SHBG were perfo rmed on female samples. Male samples were analyzed for total and non-S HBG-bound testosterone, dihydrotestosterone, androstenedione, and dehy droepiandrosterone sulfate. Two aliquots from each pool were assayed t wice in each of two labs, All assays except SHBG in one lab used RTA p rocedures. Reliability was assessed by variance components analyses an d estimated coefficients of variation (CVs). Validity was assessed by comparing observed measurements versus expected values based on known dilution ratios. For the testosterone and dihydrotestosterone assays, CVs were usually less than 10%, For estradiol and progesterone, CVs we re usually less than 15%. Assays with larger estimated CVs included an drostenedione, dehydroepiandrosterone sulfate, estrone, and estrone su lfate. Absolute levels differed markedly between labs for most assays. Observed measurements generally agreed with values expected from the dilution ratios. A notable exception was the estrone assay at the loa est dilution level, where observed measurements were 2-4 times those e xpected. A similar but less pronounced overestimation bias for the low levels of estradiol was also suggested. This intra- and interlaborato ry variability and apparent low dilution overestimation should be acco unted for in studies relating hormones to cancer risk, especially thos e involving children and postmenopausal women.