Reproducibility studies and interlaboratory concordance for androgen assays in female plasma

We conducted studies to determine the magnitude and sources of variability in androgen assay results and to identify laboratories capable of performin g such assays for large epidemiological studies. We studied androstanediol (ADIOL), androstanediol glucuronide (ADIOL G), androstenedione (ADION), and rosterone glucuronide (ANDRO G), androsterone sulfate (ANDRO S), dehydroepi androsterone (DHEA), dehydroepiandrosterone sulfate (DHEA S), dihydrotestos terone (DHT), and testosterone (TESTO), A single sample of plasma was obtai ned from five postmenopausal women, five premenopausal women in the midfoll icular phase of the menstrual cycle, and five women in the midluteal phase, divided into aliquots, and stored at -70 degrees. Four sets of two coded a liquots from each woman were then sent to participating labs for analysis a t monthly intervals over 4 months. Using the logarithm of assay measurements, we estimated the components of v ariance and three measures of reproducibility. The usual coefficient of var iation is a function of the components that are under the control of the la boratory. The intraclass correlation between measurements for a given indiv idual is the proportion of the total variability that is associated with in dividuals. The minimum detectable relative difference is important to evalu ate study feasibility, Results suggest that a single sample of ADIOL G, DHE A, DHEA S, and ANDRO G (with two lab replicates per sample) can be used to discriminate reliably among women in a given menstrual phase or menopausal status. The results for DHT, TESTO, ADION, and ANDRO S are more problematic and suggest that the present measurement techniques should be used with ca re, especially with midluteal phase women, The results for ADIOL suggest th at this assay is not yet ready for use in epidemiological studies.