[Collaborative tests of steroid hormone determinations: accuracy and precision of analytic results]

In the years 1977 to 1981, 14 quality-control surveys for the determination of steroid hormones were performed in cooperation with the Deutsche Gesellschaft für Klinische Chemie. Hereby the laboratories participating could in each case analyze the following steroids: aldosterone, cortisol, oestradiol-17 beta, oestriol, progesterone, and testosterone. In the light of the results an investigation was made as to whether, in the course of time, an improvement in the accuracy or in the precision of the determinations had been attained, and to what extent the determinations depend on the qualities of the test material. A clear improvement in the accuracy of the results of the analyses could only be ascertained for oestradiol-17 beta. For aldosterone and cortisol, values were found in pool-plasma whose medians were significantly above the definitive values. An improvement in precision could be noted especially with oestradiol-17 beta and to lesser degrees with cortisol and oestriol. The kind of test material--plasma which contained only the hormones to be analyzed on the one hand, and, on the other hand, pool-plasma, which also contained all endogenous hormones--had no influence on the precision of the results from various laboratories. Low concentrations of the individual steroids led--on the basis of the methodological principle of radioimmunoassays--in almost all cases to a reduced interlaboratory precision in regard to values. The accuracy of the analysis values was considerably impaired only with aldosterone and oestradiol-17 beta by low concentrations: the medians here were in part twice as high as the definitive values.