Selection of calibration standard concentrations for determination of intact-PTH by immunoradiometric assay

The routine determination of parathyroid hormone (PTH) by immunoradiometric assay (IRMA) has been studied. Concentrations of standards have been adequate to the clinical range in order to reduce errors. Proposed standards were tested by the calculation of different quality parameters. Recoveries of sample concentrations were estimated for different experimental alterations (methodological errors, reagent degradation, or changes in background response). Finally, inter-assays demonstrated that reproducibility of samples with concentrations in the critical clinical limits was improved. The results confirmed that the proposed selection provided a more robust method and it is possible to extrapolate to other clinical immunoassays.