J. Claflin1, A. Dhir1, N. M. Espinosa1, A. G. Antunez1, D. T. Hughes1,2 1University Of Michigan,Medical School,Ann Arbor, MI, USA 2University Of Michigan,Department Of Surgery,Ann Arbor, MI, USA
Introduction:
Intraoperative parathyroid hormone (IOPTH) monitoring is used to predict biochemical cure during parathyroidectomy. However, there is variability in the IOPTH criteria used to define biochemical cure during surgery. We hypothesize that using a lowest IOPTH value that is more restrictive than the typical criteria of 50% drop from pre-excision and into the normal range will better predict post-operative normocalcemia.
Methods:
This is a retrospective study of 2,706 patients with primary hyperparathyroidism who underwent parathyroidectomy with IOPTH monitoring at a single-center from 1999 to 2014. We used multivariate logistic regression analysis to measure associations between the lowest IOPTH level and persistence of primary hyperparathyroidism following parathyroidectomy in order to define the optimal IOPTH level to best predict cure after surgery.
Results:
Forty-eight (1.8 %) patients had persistent hyperparathyroidism after parathyroidectomy. After adjusting for patient factors and disease severity the lowest IOPTH was a significant predictor of post-operative normocalcemia (OR= 1.18 per 10 pg/mL increase, 95% CI = 1.11-1.25, p < 0.01). Patients with a lowest IOPTH above the normal range (>65 pg/mL) had significantly higher persistence rates compared to patients with an IOPTH in or below the normal range (6.3% vs 1.4%, p < 0.01) (Figure 1). Furthermore, patients with a lowest IOPTH from 20-40 pg/mL had reduced incidence of persistence compared to patients with lowest IOPTH 40-65 pg/mL (1.4% vs 3.4%, p <0.01). Patients with lowest IOPTH 0-20 pg/mL did not have significantly reduced incidence of persistence compared to patients with lowest IOPTH 20-40 pg/mL (0.7% vs 1.4%, p = 0.09).
Conclusion:
During parathyroidectomy for primary hyperparathyroidism, patients with a 50% drop from pre-excision PTH and a lowest IOPTH level below 40 pg/mL had lower rates of persistent primary hyperparathyroidism than patients who met only the traditional criteria of a 50% drop from pre-excision PTH and a final IOPTH level in the normal range (<65 pg/mL). Our analysis shows no additional benefit to achieving an IOPTH level below 20 pg/mL.
