Background: Intraoperative assays of parathyroid hormone (PTH) in the surgical management of hyperparathyroidism have been limited by an extended "turnaround" time, making it impractical for the operating surgeon. With our modification of a standard immunoradiometric assay for intact PTH, results are reported in 12 minutes. The operative usefulness and the ability of this "quick PTH" assay to predict postoperative serum calcium levels are reported here.
Methods: Quick PTH levels from whole blood samples taken 10 minutes after excision of hyperfunctioning parathyroid glands were compared with preoperative and preexcision samples in patients undergoing 63 parathyroidectomies. Patients were divided into two groups with assay incubation times of 10 and 6 minutes. The latter was clearly not sensitive enough and resulted in a 20% false-negative rate. However, with a 10-minute incubation time, a decrease of 54% or more in quick PTH levels resulted in postoperative normocalcemia in patients with primary hyperparathyroidism.
Results: With these criteria used to predict the postoperative return to normocalcemia in 29 patients with primary hyperparathyroidism, the quick PTH assay had a sensitivity of 96%, specificity of 100%, and overall accuracy of 97%.
Conclusions: The quick PTH assay was especially helpful in predicting postoperative calcium levels when multiple excisions were necessary to remove all hyperfunctioning tissue or some normal parathyroid glands were not visualized.