Applicability of a shortened interpretation model for intraoperative parathyroid hormone monitoring in patients with primary hyperparathyroidism in an endemic goiter region

BACKGROUND: In primary hyperparathyroidism (pHPT), quick intraoperative parathyroid hormone monitoring (IOPTH) is performed to predict complete excision of hyperfunctioning tissue and therefore cure. In recent years, efforts have been made to make this prediction more accurate and to shorten the duration of the test, respectively, and therefore reduce waiting and total operating time. The aim of this study was to evaluate the practicability and safety of a time-reduced criterion (decline ≥ 35% after 5 min) in a large cohort of patients. METHODS: In an 11-year period, all patients operated for pHPT were analyzed. After preoperative localization studies, hyperfunctioning parathyroid tissue was removed and IOPTH monitoring was performed. Intraoperatively, a decline of ≥50% from baseline 10 min after excision of the gland predicted cure. The performance of an interpretation model, using an earlier PTH level was analyzed retrospectively (decline ≥ 35% from baseline 5 min after excision). Differences in sensitivity, specificity, positive/negative predictive value and accuracy were calculated. RESULTS: According to the inclusion criteria, 1018 patients were analyzed. IOPTH predicted cure in 854 patients (83.9%) 10 min after gland excision with a false positive decline in 13 patients (1.5%). Applying the modified criterion (≥35% decline within 5 min), 814 patients (80%) showed an appropriate decline (false positive in 18 [2.2%]). Overall, multiple gland disease would have been missed in 7 patients. McNemar’s test showed a significantly lower sensitivity, specificity and accuracy applying the “35%” criterion. CONCLUSIONS: In an endemic goiter region, a criterion, demanding a ≥ 35% decline 5 min after excision can not be recommended for IOPTH monitoring in patients with pHPT.