Qualitative and quantitative comparison of different commercially available 1–84 parathyroid hormone proteins to the WHO international standard 95/646 using orthogonal methods

Abstract

Relative quantitation methods rely on the use of reference substances to determine the content of samples. The aim of this study was to compare 1–84 parathyroid hormone (PTH) standards from different manufacturers to the WHO international standard 95/646. CE and LC with UV detection were investigated as quick and inexpensive quantitation methods, with an emphasis on selectivity between intact 1–84 PTH and its oxidized forms. Both methods were fully validated according to ICH Q2R1. Moreover, method performance was also evaluated according to guidelines defining the maximum allowable measurement uncertainty (MU) of a biological parameter from its intraindividual variation (CVI), as well as the proportion of that MU devoted to the reference material. This study highlighted the fact that some 1–84 PTH standards have a content that is actually twice as high as the one stated on the label, which was confirmed by an amino acid analysis investigation. Our approach offers a quick and inexpensive way to estimate the content of 1–84 PTH standards.