Intraoperative parathyroid hormone assay improves outcomes of minimally invasive parathyroidectomy mainly in patients with a presumed solitary parathyroid adenoma and missing concordance of preoperative imaging.

OBJECTIVE: Intraoperative parathyroid hormone assay (IOPTH) is often used during minimally invasive parathyroidectomy (MIP) for primary hyperparathyroidism (pHPT). However, several investigators have reported conflicting outcomes, throwing doubt on the real influence of this adjunct on surgical decision-making. The aim of this study was to determine the impact of routine use of IOPTH on the success rate of MIP as the primary outcome, and whether it value-added to surgical decision-making during the operations at our institution.

DESIGN: The results of MIP were determined on postoperative follow-up in 177 consecutive patients with pHPT and compared with the results of preoperative imaging, findings at surgery and the value-added accuracy of IOPTH in surgical decisions.

PATIENTS: All 177 patients had biochemically documented pHPT and all were referred for first-time surgery.

MEASUREMENTS: Group 1 patients (n = 62) underwent a unilateral neck exploration (UNE) without IOPTH, and group 2 patients (n = 115) underwent MIP (either video-assisted or open) with IOPTH. The primary outcome was the cure rate, whereas the secondary outcome was the value-adding of IOPTH to surgical decision-making during MIP.

RESULTS: Of the group 1 vs. 2 patients, 57/62 (91.9%) vs. 114/115 (99.1%) were cured (P = 0.01). Five (8.1%) of the group 1 patients were hypercalcaemic postoperatively, owing to an additional, overlooked, hyperfunctioning parathyroid gland, whereas among the 115 group 2 patients, 104 (90.4%) underwent resection of a single parathyroid adenoma, met the Miami criterion, and were cured. The remaining 11 (9.6%) patients did not have an adequate reduction in parathyroid hormone levels and underwent further neck exploration, with resection of additional hyperfunctioning parathyroids in nine of them. One group 2 patient was not cured. However, a decrease of less than 50% of intraoperative parathyroid hormone (iPTH) assay correctly identified the risk of persistent disease in that patient. Another patient in group 2 had a false-negative IOPTH result. The value-added accuracy of IOPTH (correct assay-based surgeon's decision of further neck exploration) was demonstrated in 3 of 78 group 2 patients with concordant results of both imaging studies vs. 7 of 37 group 2 patients with only one positive imaging study, or 3.8 vs. 18.9% of patients (P = 0.007).

CONCLUSIONS: Routine use of IOPTH significantly improves cure rates of MIP in comparison to open image-guided UNE without IOPTH. It is a valuable adjunct in surgical decision-making, allowing for intraoperative recognition and resection of additional hyperfunctioning parathyroid tissue missed by preoperative imaging studies. IOPTH offers substantial value-adding to surgical decision-making, particularly in patients with only one positive imaging study result, and significantly improves the success rate of MIP in these patients. However, in patients with concordant results of two imaging studies, the assay offers significantly lower value-adding to surgical decisions, as a vast majority of patients are cured after removal of a two-image-indexed parathyroid lesion. Despite this, we strongly advocate routine use of IOPTH in all patients undergoing MIP, as this adjunct offers maximum safety for the patient and confidence for the surgeon.