Accuracy of PTH assay and corrected calcium in early prediction of hypoparathyroidism after thyroid surgery

Abstract

Objective To evaluate the accuracy of the intraoperative parathyroid hormone (ioPTH) and 6-hour PTH (6hPTH) assay in predicting transient hypoparathyroidism after thyroidectomy. Study Design A nonrandomized prospective study was conducted on patients undergoing thyroid surgery. Subjects and Methods Of 138 patients undergoing thyroid surgery, intraoperative PTH was measured 10 minutes after gland removal. Serum calcium, magnesium, inorganic phosphorus, albumin, and PTH levels were assayed 6 and 16 hours after surgery and daily until patient discharge. Results The development of postoperative hypocalcemia was associated with low ioPTH ( P < 0.0001) and 6hPTH ( P < 0.0001) values, and the decline of PTH from baseline ( P < 0.0001). The cutoff for percentage decline of ioPTH and 6hPTH (55.7% and 379%, respectively) was more accurate than an absolute value. Accuracy, and positive and negative predictive values were 88 percent, 63 percent, and 100 percent for ioPTH and 75 percent, 46 percent, and 100 percent for 6hPTH, respectively. Conclusion With the use of ioPTH decline in association with 16-hour corrected calcium, it is possible to distinguish early normocalcemic patients from hypocalcemic ones in most cases.