Lnterlaboratory comparison of radioimmunological parathyroid hormone determination*

An inter‐laboratory study of serum immuno‐reactive PTH (iPTH) determinations using standardized sera has been performed in order to check the value of the assays for the diagnosis of hyperparathyroid states, The results demonstrate: (1) that most of the cooperating laboratories (eleven of twelve) were able to discriminate between normal and grossly elevated PTH‐values; (2) that direct comparison of values from different laboratories indicates very poor agreement; (3) that PTH values cannot be interpreted without a description of the characteristics of the assay used; (4) that the introduction of standard sera is advantageous and should be undertaken; (5) that determination of iPTH in serum samples is far from being a routine method when compared with radioimmunoassays for hormones like insulin, growth hormone, etc.; the difficulties being due to lack of standardized reagents and peculiarities in the metabolism of the hormone.