Influence of Preanalytical Factors on the Immulite Intact Parathyroid Hormone Assay

[摘要] Preanalytical factors that affect parathyroid hormone (PTH) concentrations are not well defined. Measured PTH concentrations in EDTA plasma may (1)(2) or may not(3) differ from those in serum. PTH has been reported variously to be stable for hours to days (1)(2)(3)(4)(5)(6). In addition, different PTH assays cross-react to various extents with biologically inactive, N-terminally truncated PTH molecules (7) that may have different stabilities. The specificity of a given immunometric assay depends on the binding sites of the anti-PTH antibodies used. So-called “intact” PTH (iPTH) assays show cross-reactivity with peptides lacking N-terminal amino acids. Assays measuring only PTH with intact NH2 termini are named CAP™; whole PTH, 3rd generation; or bioactive PTH assays (7).In 2001, DPC introduced a reformulated iPTH sandwich assay (starting with lot no. 106) in which the polyclonal tracer antibody had been replaced by a monoclonal antibody raised against an epitope within the first 34 amino acids of PTH. With this new method, reference intervals and, in particular, PTH concentrations measured in serum samples of dialysis patients are lower (data not shown). In March 2003, DPC reported underrecovery of PTH with this method (8), and a new lot of raw materials was introduced, starting with assay lot no. 112. The calibration for the Immulite analyzer was adjusted at assay lot no. 113 (8). Shortly before this, we had found …

[学科分类] 过敏症与临床免疫学