A-048 Reference Interval and Clinical Performance Studies for Vitros® Immunodiagnostic Products Intact PTH II Assay to Aid in Diagnosis of Calcium and Parathyroid Disorders and Intraoperative Testing

Abstract

Abstract Background Intact parathyroid hormone (iPTH) measurements aid in the differential diagnosis of hypercalcemia, hypocalcemia, and parathyroid disorders. The National Academy of Clinical Biochemistry has established guidelines for intraoperative PTH testing to monitor surgical success during parathyroidectomies. Studies were conducted to define the reference interval and clinical performance of the Vitros Immunodiagnostic Products Intact PTH II (Vitros iPTH II) assay, using samples from healthy individuals and patients with conditions commonly requiring iPTH testing, including intraoperative cases. Methods The reference interval study was conducted in accordance with Clinical and Laboratory Standards Institute (CLSI) guideline EP28-A3c in serum samples from 134 healthy individuals. For the clinical performance study, serum samples from individuals with hypoparathyroidism, primary hyperparathyroidism, chronic renal failure (secondary or tertiary hyperparathyroidism), hypercalcemia, hypercalcemia of malignancies, and hypocalcemia were tested. Intraoperative samples used were collected from parathyroidectomy patients in series at each surgical timepoint along with the standard plasma samples used to determine surgical success. Results The reference samples were composed of 134 serum donors that met all inclusion/exclusion criteria for healthy donors and had a normal test result on calcium, TSH, alkaline phosphatase, creatinine, and phosphate assays. The reference interval for iPTH was determined to be 14.2-75.2 pg/mL. The results in various disease states demonstrated the clinical performance of the Vitros iPTH II assay. Of 32 intraoperative sample series included in the study, three samples demonstrated no intraoperative decrease in iPTH due to surgical failures. Consistent with the goal of the parathyroidectomy procedure, at least a 50% decrease in iPTH was observed between the presurgical and post-excision samples in all other sample series. The clinical concordance with the Roche PTH assay used intraoperatively in these procedures was 100%. Conclusions Defining the reference interval for a normal healthy population and results from the intended use population demonstrated that the Vitros iPTH II assay can be used as an aid in the diagnosis of calcium and parathyroid disorders and intraoperative testing.