12410 Intra-operative Parathyroid Hormone Monitoring: Comparative Evaluation Of Sampling Sites And Assay Methods

Abstract

Abstract Disclosure: R. Kwayess: None. S. Ajjour: None. M. Rahme: None. M. Assaad: None. J. Abbas: None. S. Jabbour-Khoury: None. R. Daher: None. E. Cavalier: None. O. Kreidieh: None. M. Chakhtoura: None. G. El-Hajj Fuleihan: None. Background: Primary hyperparathyroidism is a common endocrine disorder increasingly managed by minimally invasive parathyroidectomy (MIP) with intra-operative parathyroid hormone (IOPTH) monitoring using 2nd generation parathyroid hormone (PTH) assay. Objective: Compare the use of central sampling versus peripheral sampling, and of 3rd as opposed to 2nd generation PTH assays’ performance. Methods: We collected preoperative baseline characteristics and laboratory values for consenting participants undergoing parathyroidectomy at our center. We then measured IOPTH levels from peripheral and central venous sites using 2nd and 3rd generation assays at various intraoperative time points. We calculated the maximal intraoperative PTH drop from highest baseline (pre-incision or pre-excision) at peripheral site and pre-excision at central site for participants who were normocalcemic at ≥ 6 months post-operatively. We used paired t-test to compare the mean % drop in IOPTH by 2nd vs 3rd generation assays, and peripheral vs central sampling. Results: Out of 88 participants enrolled, 63 had follow-up data at 6 months or beyond and normal serum calcium level (9.41 ± 0.43 mg/dL). Mean age was 56.16 ± 11.5 years, 77.8% females and 47.6% had osteoporosis or osteopenia. Pre-operative mean values were: serum calcium 10.94 ± 0.73 mg/dL, ionized calcium 5.6 ± 0.68 mg/dL, PTH 131.93 ± 120.1 pg/mL and creatinine 0.77 ± 0.19 mg/dL. The majority of patients underwent excision of one abnormal gland (79.4%). On average, 57.3% of patients had the highest PTH drop at 10 mins, 32.7% beyond 10 minutes, and 9.7% at 5 minutes, regardless of assay type and site. Median PTH decrements were 81% and 83.8% for 2nd generation assay, and 86.5% and 89% for 3rd generation assays, at peripheral and central sites, respectively. There was no significant difference in the PTH drop comparing central to peripheral sites using either assay. However, 3rd generation assays displayed a higher drop compared to 2nd generation assay, for both central and peripheral sites (p-value <0.001). Discussion/Conclusion: Our study shows no difference in % drop between peripheral and central sampling, using either 2nd or 3rd generation assays. Central PTH sampling is commonly used by surgeons because of ease of access, while applying the Miami criterion. However, the drop in median 3rd generation PTH level was higher compared to the 2nd generation assay, regardless of the sampling site. Our findings suggest the necessity of defining larger PTH drop cut-off values for 3rd generation PTH assay than the commonly used Miami criterion.