A Retrospective Study of the Impact of Intraoperative Intact Parathyroid Hormone Monitoring During Total Parathyroidectomy for Secondary Hyperparathyroidism

The study aimed to evaluate the diagnostic accuracy of intraoperative intact parathyroid hormone (IO-iPTH) in patients with secondary hyperparathyroidism (HPT). The cut-off for IO-iPTH monitoring remains unknown. This was a single-center retrospective review of 226 consecutive patients (107 males and 119 females) who underwent parathyroidectomy data for secondary HPT between May 2010 and March 2014. The predetermined cut-off for IO-iPTH was a 70% IO-iPTH drop from baseline 10 minutes after total parathyroidectomy and thymectomy. We used <60 pg/mL iPTH value on postoperative day 1 (POD1) as an indicator of successful removal of parathyroid glands and reviewed the frequency of reoperation other than in autografted sites during the observation period. This study was based on the Standards for the Reporting of Diagnositic accuracy compliant. The reoperation rate in patients with >60 pg/mL iPTH value (POD1) was significantly higher than that in patients with <60 pg/ mL iPTH value (POD1), (13.0% versus 0.5% P1⁄4 0.003). Sensitivity, specificity, and accuracy of >70% IO-iPTH drop were 97.5%, 52.2%, and 92.9%, respectively, this criterion was demonstrated to be beneficial in 26 patients. In 5 patients, <70% IO-iPTH drop was observed and further exploration enabled sufficient removal of parathyroid glands. In 21 patients, although fewer than 4 parathyroid glands were removed after enough explorations, >70% IO-iPTH drop enabled termination of operations and iPTH value (POD1) was <60 pg/mL. An iPTH value of <60 pg/mL (POD1) was a good predictor for successful parathyroidectomy. A 70% IO-iPTH drop from the baseline was appropriate to determine sufficient parathyroid gland removal aga, MD, PhD, M MD, d Takaaki Kobayashi, MD, PhD Abbreviations: FN = false negative, FP = false positive, HPT = hyperparathyroidism, IO-iPTH = intraoperative intact parathyroid hormone, iPTH = intact parathyroid hormone, NPV = negative predicitive value, POD1 = postoperative day 1, PPV = positive predicitive value, TN = true negative, TP = true positive. INTRODUCTION I ntraoperative intact parathyroid hormone (IO-iPTH) monitoring is common in parathyroidectomy for primary hyperparathyroidism (HPT), particularly for minimally invasive procedures, and several criteria have been established for the same. Marcin et al evaluated the efficacy of various IOiPTH monitoring criteria and concluded that the Miami criterion of >50% drop from the highest intraoperative PTH values at 10 minutes after excision has the best sensitivity, specificity, and accuracy. Although several criteria have been proposed for IO-iPTH monitoring in patients with secondary HPT, no consensus has been reached. Using the Quick-Intraoperative Bio-Intact PTH assay (Nichols Institute Diagnostics, San Clemente, CA), a number of criteria for parathyroidectomy in patients with secondary HPT has been reported. This assay was quick and reliable, taking only 15 to 20 minutes to obtain results. Moreover, the established criteria were excellent, enabling the efficient removal of all parathyroid glands during parathyroidectomy for secondary HPT. Unfortunately, this kit is no longer available, therefore, iPTH is now widely used to evaluate the parathyroid function. A limitation of iPTH is that it consists of many fragments with varying half-lives and proportions. Consequently, IO-iPTH monitoring has rarely been reported. For secondary HPT, successful parathyroidectomy should be performed to avoid continued stimulation by the residual gland tissue that might cause recurrent secondary HPT in the context of impaired renal function. However, embryological and anatomical features make it difficult to perform successful parathyroidectomy. Furthermore, in 13% of patients, more than 4 parathyroid glands exist, and ectopic glands exist in the thymus, mediastinum, thyroid gland, and upper neck. Thus, if the sufficient removal of parathyroid glands can be intraoperatively confirmed, it may be possible to avoid further unnecessary explorations and to prevent operative failure due to missed supernumerary glands. To date, only a few studies on a small number of patients have reported criteria to determine operative success using IOTherefore, we aimed to retrospectively criteria for parathyroidectomy in a large h secondary HPT. www.md-journal.com | 1