Intraoperative total serum calcium levels,unlike intraoperative intact PTH levels,do not correlate with cure of hyperparathyroidism

BACKGROUND: Intraoperative intact parathyroid hormone (iPTH) monitoring is useful in the operative management of hyperparathyroidism. Recent studies suggest that measurement of intraoperative total serum calcium (TSC) levels may be a more cost effective and readily available method of intraoperative guidance during neck dissection than iPTH levels, the gold standard. We compared the accuracy of intraoperative TSC to iPTH in predicting surgical cure during parathyroidectomy. PATIENTS AND METHODS: From September 1, 2001 to October 31, 2002, 88 parathyroidectomies were performed. iPTH and TSC were measured at the start of the operation, and at 5 and 10 min after gland removal. Data were compared, and trends were analyzed with respect to removal of abnormal parathyroid tissue as confirmed by pathology. One-way analysis of variance was used to determine if decreases in TSC were significant. RESULTS: The mean baseline iPTH level (418 +/- 610 pg/ml) dropped by 70% 5 min after removal of the abnormal glands (86 +/- 102 pg/ml) and by 85% at 10 min (39 +/- 39 pg/ml). The mean baseline TSC level (10.0 +/- 0.8 mg/dl) dropped by 4% at 5 min after removal of the abnormal glands (9.6 +/- 0.9 mg/dl) and remained at 4% at 10 min (9.6 +/- 0.8 mg/dl). iPTH dropped by > or =50% in 73 patients (83%) at 5 min and in 87 patients (99%) at 10 min after gland resection. TSC decreased below baseline at 5 min and remained below baseline at 10 min in only 47 patients (54%). In the remaining patients, intraoperative TSC changes were less predictable and did not respond consistently to resection of abnormal glands. CONCLUSIONS: The decreases in TSC during parathyroidectomy, if present, are minimal. Unlike iPTH levels, TSC levels do not consistently decrease at 5 and 10 min after gland resection. While attractive in terms of cost and availability, intraoperative TSC levels are not clinically reliable in confirming removal of abnormal parathyroid tissue.