A-056 Ex-Vivo Parathyroid Aspiration in Parathyroidectomy: Correlation with Histopathology and Biochemical Outcomes in Single- and Multi-glandular Primary Hyperparathyroidism

Abstract Background Primary hyperparathyroidism (PHPT) is the third most common endocrine disorder in the United States. Surgical management of primary hyperparathyroidism frequently incorporates intraoperative testing to confirm the presence of parathyroid tissue. At our institution, we utilize ex-vivo aspiration of excised parathyroid tissue, followed by intraoperative parathyroid hormone testing (aIOPTH), which is a rapid and highly sensitive method for distinguishing parathyroid from surrounding tissues. Despite growing adoption, there is limited research on standardized aIOPTH protocols, their relationship with final histopathological results, and their impact on patient outcomes. Various techniques have been described for this purpose, but the literature offers limited guidance on the recommended approach for different surgical scenarios. This study seeks to offer guidance on recommendations for adenoma or multiglandular disease when imploring aIOPTH. Methods This retrospective study was conducted at a tertiary academic medical center and included patients who underwent parathyroidectomy with aIOPTH testing between June 2023 and January 2025. The quantitative aIOPTH values were categorized as either ‘positive’ or ‘negative’ based on absolute thresholds of 500 and 5,000 pg/mL. These categorized results were compared to the final histopathological diagnoses of the excised tissue, and performance metrics were calculated. Separate analyses were conducted for patients with adenoma versus those with multiglandular disease. Results A total of 161 unique aIOPTH specimens which had a preoperative diagnosis of PHPT were analyzed. With the 500 pg/mL threshold, sensitivity was 97% and PPV was 97%. Using the 5,000 pg/mL threshold, sensitivity decreased to 86%, while PPV increased to 99%. In the subgroup of patients with multiglandular disease, 93 unique aIOPTH specimens were analyzed. In this subgroup, the sensitivity and PPV were 98% and 96% for the 500 pg/mL cutoff, and 84% and 100% for the 5,000 pg/mL cutoff, respectively. At the time of this analysis, 96.6% of patients with who had six-month postoperative calcium testing (n=29) demonstrated durable biochemical cure. Conclusion The application of absolute cutoffs in aIOPTH testing protocols demonstrates clinical performance consistent with existing literature. Lower PTH cutoffs enhance sensitivity without a substantial reduction in PPV for patients with multiglandular disease. Additionally, aIOPTH shows comparable performance in patients with multiglandular disease. These findings support the use of ex-vivo aspiration for intraoperative parathyroid testing as an effective decision-making tool in parathyroidectomy and lead to guidance for adenoma and multiglandular disease.