POS-551 INTRAOPERATIVE PLASMA (1-84) PTH LEVELS ARE BETTER THAN INTACT PTH FOR ASSESSING THE SUCCESS OF PARATHYROIDECTOMY IN UREMIC HYPERPARATHYROIDISM PATIENTS

Abstract

Parathyroidectomy (PTX) is the most effective treatment in severe secondary hyperparathyroidism (SHPT) patients with chronic kidney disease (CKD). Complete removal of all parathyroids is essential for successful PTX. Excessive or ectopic parathyroids are related with persistent SHPT, which occurs up to 25% of cases. Now the most commonly used second-generation intact parathyroid hormone (iPTH) assay can not only recognize (1-84)PTH, also named as whole PTH (wPTH), but also large C-terminal PTH. While the third-generation PTH assay can measure (1-84)PTH specifically. This provides a possibility of diagnostic accuracy for successful PTX by intraoperative (1-84)PTH because of its higher specificity and shorter half-life, however, there is no relevant report. Here we compared the predictive value of intraoperative plasma (1-84) PTH and iPTH levels in order to improve the safety and efficiency for PTX prospectively. We included 100 healthy controls, 162 stage 5 CKD patients without SHPT, 214 PTX patients because of SHPT. Plasma iPTH and (1-84)PTH levels were measured before incision (io-iPTH0, io-[1-84]PTH0), 10min (io-iPTH10, io-[1-84]PTH10) and 20min (io-iPTH20, io-[1-84]PTH20) after removing all parathyroids. Reduction percentage of PTH at 10min and 20min were calculated (io-iPTH10%, io-[1-84]PTH10%, io-iPTH20%, io-[1-84]PTH20%). Within one week after PTX, patients with serum iPTH<50pg/ml were classified as successful PTX, and patients with serum iPTH≥300pg/ml were defined as persistent SHPT. Patients would be followed up in 6 months when serum iPTH levels between 50-300pg/ml, serum iPTH＜300pg/ml subgroup was defined as successful PTX, and those whose serum iPTH≥300pg/ml were persistent SHPT(Fig.1). The receiver operating characteristic (ROC) curve was used to determine cut-off values for predicting surgical outcome. Accurate diagnosis was expressed by sensitivity, specificity, and area under the ROC curve (AUC). Baseline (1-84)PTH levels in controls, non-PTX and PTX patients were 22.10(15.36-31.31)pg/ml, 94.51(52.31-190.70)pg/ml and 850.90(595.00-1269.00)pg/ml. In PTX group, there were 187 successful PTX(87.38%), 19 persistent SHPT (8.88%), and 8 patients(3.74%) were lost to follow-up. In successful PTX subgroup, there were 5 patients had five parathyroids, 1 patient had two parathyroids, and 7 patients had three parathyroids. There was no significant difference between successful PTX and persistent SHPT subgroup on plasma io-iPTH10 levels. Compared with successful PTX group, persistent SHPT patients had higher io-(1-84)PTH10, io-iPTH20 and io-(1-84)PTH20 levels (P＜0.001). ROC curve revealed io-(1-84)PTH10%＞86.64% (AUC 0.77, sensitivity 55.10%, specificity 94.70%), and io- (1-84)PTH20%＞87.46% (AUC 0.92, sensitivity 84.00%, specificity 94.70%) could predict successful PTX. Sensitivity of io-iPTH20% and io-(1-84)PTH20% were higher than those at the time-point of 10min. Compared with iPTH10% and iPTH20%, the predictive ability of io-(1-84)PTH10% and io-(1-84)PTH20% were higher (sensitivity: 55.10% vs 51.90% and 84.00% vs 73.30%; specificity: 94.70% vs 89.50% and 94.70% vs 89.50%)(Fig. 2). Intraoperative reduction percentage of plasma (1-84)PTH level is superior to iPTH for accurate evaluating successful PTX, especially at the time-point of 20min after all cervico-thoracic parathyroids were resected.