R. Teo1, J. C. Farrá1, O. P. Roque1, A. R. Marcadis1, J. I. Lew1 1University Of Miami,Division Of Endocrine Surgery,Miami, FL, USA
Introduction: Intraoperative parathormone (ioPTH) monitoring is widely used to predict operative success for targeted parathyroidectomy (PTX) using a >50% PTH drop criterion in patients with primary hyperparathyroidism (pHPT). However, the significance of ioPTH “spikes” at the pre-excision measurement during targeted PTX, commonly from gland manipulation by the surgeon, remains unclear with the assertion that multigland disease (MGD) may be missed. This study compares targeted PTX with and without ioPTH spikes using the >50% PTH drop criterion, and determines the effect of ioPTH spikes on operative outcome.
Methods: A retrospective review of prospectively collected data of 783 patients who underwent targeted PTX guided by ioPTH monitoring for pHPT confirmed by elevated serum calcium and parathormone (PTH) levels was performed. All patients had >6 months of follow-up with a mean of 42 months. When a >50% drop from the highest pre-incision or pre-excision PTH level was achieved at 10 minutes intraoperatively, the operation was completed. An ioPTH ‘spike value' (SV) was calculated by subtracting the pre-incision ioPTH value (PI) from the pre-excision ioPTH value (PE) (SV = PE – PI). An ioPTH spike was defined as having a positive SV ≥ 9 pg/ml (≥10th percentile of positive SV). Operative success was defined as eucalcemia ≥6 months after PTX. Operative failure was defined as elevated calcium and PTH levels <6 months after PTX. MGD was defined as persistently elevated ioPTH levels despite removal of one hypersecreting gland, or when removing a single parathyroid gland resulted in operative failure.
Results: Overall, 256 of 783 patients (33%) with ioPTH spikes had a significantly higher rate of MGD (n=21/256, 8% vs. n=21/527, 4%, p<0.05) and bilateral neck exploration (BNE) (n=44/256, 17% vs. n=61/527, 12%, p<0.05) compared to patients without ioPTH spikes, respectively. Accordingly, more ioPTH spike patients also did not meet the >50% PTH drop criterion from the highest PI or PE value at 10 minutes (n=42/256, 16% vs. n=44/527 8%, p<0.05) compared to patients without ioPTH spikes. Of the 42 patients with ioPTH spikes without a >50% PTH drop, 21 underwent BNE (14 met criteria for MGD and 7 had unnecessary BNE) and 21 did not undergo BNE (2 met criteria for MGD). Overall, there were no differences between PTX patients with ioPTH spikes and no-spikes in terms of operative success (97% vs. 98%), operative failure (3% vs. 2%) or recurrence rates (0.8% vs. 1.0%), respectively.
Conclusion: Although patients who underwent targeted PTX with ioPTH spikes had a higher rate of MGD requiring BNE, operative success was similar to those patients without ioPTH spikes. While the presence of ioPTH spikes may increase suspicion for MGD, the ability of targeted PTX guided by ioPTH monitoring in predicting operative success is not affected by spikes and reaffirms the utility of the >50% PTH drop criterion.