Clinical Information

Parathyroid hormone (PTH) values should be interpreted in conjunction with serum calcium and phosphorus levels, and the overall clinical presentation and history of the patient. The carboxyl-terminal (PTH-C) fragment 7-84, which accumulates in kidney failure, shows substantial cross-reactivity in this assay. Healthy population reference ranges, therefore, do not apply in kidney failure. Some overlap of intact PTH values does exist for patients with various parathyroid disorders. Measurement of intact PTH is useful in differentiating between hypercalcemia due to hyperparathyroidism and hypercalcemia of malignancy. However, the assay is not intended as, and should not be relied upon as, a diagnostic indicator of malignancy. It is extremely important to ensure that patient samples have been handled and stored correctly. Incorrect handling of samples will result in a loss of intact PTH. For assays employing antibodies, the possibility exists for interference by human anti-animal antibodies (i.e., heterophile antibodies) in the patient sample. Patients who have been regularly exposed to animals or have received immunotherapy or diagnostic procedures utilizing immunoglobulins or immunoglobulin fragments may produce antibodies, (e.g., HAMA), that interfere with immunoassays. This may falsely elevate or falsely decrease the results.