Preanalytical Factors in the Measurement of Intact Parathyroid Hormone with the DPC IMMULITE Assay

Abstract

Intact parathyroid hormone (iPTH) is commonly measured with two-site immunometric assays. The DPC IMMULITE 2000 assay (Diagnostics Products Corporation) measures iPTH by a chemiluminescence reaction with a monoclonal murine capture antibody and a polyclonal caprine signal antibody conjugated to alkaline phosphatase. Accurate and precise iPTH measurements are needed for the correct triage of individuals with hyper- or hypocalcemia and for the evaluation of PTH function in bone and mineral disorders (1)(2). In end-stage renal failure, iPTH measurements are commonly used to determine medical management (administration of vitamin D) and surgical therapeutic options (subtotal parathyroidectomy for extreme hyperparathyroidism) (3)(4). Collection of whole blood into EDTA-containing sample tubes offers increased iPTH stability at room temperature (5) compared to serum samples (6) and is recommended by the manufacturer of the DPC IMMULITE 2000 iPTH assay. However, insufficient sample volume can lead to increased final EDTA concentration in the sample-reagent mixture, causing chelation of metallic cations, and this can affect the activity of the alkaline phosphatase label used …