Clinical and laboratory evaluation of a two-site immunoradiometric assay for intact parathyroid hormone.

The analytical performance and clinical utility of a direct immunoradiometric assay (IRMA) for intact 1-84 human parathyroid hormone (PTH) was evaluated. The assay is available commercially (Allégro intact PTH, Nichols Institute) and utilises two affinity purified region-specific antisera against either 1-34 (radiolabelled antibody) or 39-84 (solid phase antibody) human PTH. High assay sensitivity (detection limit, 1.4 pg 1-84 PTH/mL) permitted the measurement of PTH in all normocalcaemic individuals studied. Elevated results were obtained in all patients (21 studied) with histologically proven primary hyperparathyroidism (PHPT) and 34 out of 35 patients with presumptive PHPT. Thirteen out of 24 patients with non-parathyroid hypercalcaemia had suppressed results, but the remainder had concentrations within the reference range.