Intraoperative parathyroid hormone analysis: A study of 200 consecutive cases

Background: Immunoassays for parathyroid hormone (PTH), with short incubati on times and results available in <15 min, have allowed-intraoperative moni toring of the success of parathyroid surgery. The purpose of this study was to evaluate the analytical performance of a rapid PTH assay and its clinic al performance in a series of 200 patients. Methods: PTH was measured with a modified immunochemiluminometric: assay wi th a 7-min incubation time (QuiCk-IntraOperative(TM) Intact PTH assay). The rapid assay was compared with,results in a central laboratory (immunoradio metric assay) in 44 EDTA-plasma specimens. The rapid assay was used intraop eratively in 200 consecutive cases with specimens analyzed before and 5-10 min after resection of the hypersecreting: parathyroid gland(s). Results: Intraassay imprecision was 12% at 28 ng/L and 11% at 278 ng/L. Reg ression analysis of results; of the; rapid PTH assay and the IRMA PTH assay in 44 parathyroidectomy patients yielded y = 1.26x - 12 ng/L, S-y\x = 26.3 ng/L, r = 0.984, and in 40 of 44 patients with values <200 ng/L, y = 1.02x + 1.9, S-y\x = 13.9, r = 0.947. In the 195 cases using intraoperative PTH testing with complete results and defined clinical outcomes, the overall ac curacy of the assay in predicting surgical success was 88% using the criter ion of a 50% decrease at 5-10 min and 97% including the subset of patients with delayed decreases of PTH. Conclusions: The rapid PTH assay had excellent analytical performance and e xcellent agreement with the PTH immunoradiometric assay and predicted the s uccess of parathyroid surgery in this large series of consecutive patients. (C) 2000 American Association for Clinical Chemistry.