[Cooperative study on the radioimmunological thyrotropin determination (hTSH) in serum (author's transl)].

This paper deals with a cooperative survey on the radioimmunoassay of thyrotropin in human serum, which was organized by the Thyroid Group of the German Society for Endocrinology. Eighteen serum specimens were to be measured in triplicates. Among the latter were 10 specimens of a hTSH standard curve, prepared in low hTSH serum, which contained approximately 1 mU/l. One of these pool sera was divided in half, and one half was enriched with 10 kU/l human chorionic gonadotropin to test for cross reactivity. One specimen las for the measurement of the non-specific binding. The count rates and the dose levels of the standard curve of each participating laboratory (N = 32), normally performed in albumin-buffer, and the count rates of the 18 unknowns were requested as results. THE CALCULATION OF THE STANDARD CURVES AND THE RECOVERy curves, the evaluation of the unknowns and the statistics were performed by spline functions, using a 48 kb FORTRAN-program on a Siemens 404/3 computer. The results demonstrated that the interlaboratory precision of 128% and the recovery rates between 50 and 926% are very unsatisfactory. However, the coefficient of variation was lowered to 31%, when the controls were read from the recovery curves, as included in the samples. In addition to this improvement of the interlaboratory precision and of the accuracy, this study showed, that the sensitivity was markedly improved by using delayed addition of tracer.