Quantification and clinical performance of serum parathyroid hormone 1-84 via immunocapture coupled to LC-MS/MS in chronic renal failure.

Accurate measurement of serum parathyroid hormone (PTH) is crucial for diagnosing and managing endocrine and osteological diseases. Conventional immunoassay methods struggle with cross reactivity issues between full-length PTH and truncated fragments or post-translationally modified forms. Both the standardization of PTH assays and the peptide's stability are concerning. This study addresses these issues by establishing an immunocapture coupled with liquid chromatography-tandem mass spectrometry (LC-MS/MS) method to precisely quantify PTH1-84. PTH1-84 was isolated from one mL serum samples by immunocapture on a polystyrene bead and eluted from matrix, then quantitated by LC-MS/MS. The results from 268 serum samples were compared to an intact PTH immunoassay. The assay's linear range was 5.0-1000.0 pg/mL. The intra-assay coefficients of variation (CVs) ranged from 3.2 % to 6.8 %, and the inter-assay CVs ranged from 4.6 % to 9.5 %. The extraction efficiencies were 98.0 %-100.5 %, with no significant matrix effects observed after internal standard correction. The correlation coefficient between LC-MS/MS and immunoassay was 0.989, but the bias between the methods was substantial. Nevertheless, the immunocapture purification coupled LC-MS/MS method offers a promising approach for accurate PTH measurement.