A Positive Parathyroid Washout May Obviate the Need for Nuclear Scintigraphy in Parathyroid Adenoma Localization: A Retrospective Study.

Background: Minimally invasive parathyroidectomy (MIP) in patients with a parathyroid adenoma (PA) requires imaging modalities for precise localization. Parathyroid hormone assay on ultrasound-guided fine-needle aspiration washout, or PTH washout, can be used for this purpose. It is unclear whether PTH washout complements traditional PA localization techniques such as a sestamibi (MIBI) scan or diminishes its need. This study aims to determine whether a positive PTH washout obviates the need for an MIBI scan in the preoperative localization of a PA.

Method: A multi-center retrospective, comparative review comprised adult patients who underwent MIP at 2 McGill University teaching hospitals between 2018 and 2022. Patients who had both PTH washout and MIBI scan for preoperative localization of PA, final histopathology reports available, and preoperative/postoperative results recorded were included in the final analysis.

Results: Of the 193 patients' charts reviewed, 87 were included in this study. Of these 87 patients, 74.7% (65/87) had a positive PTH washout result. Among those, MIBI correctly detected 90.8% (59/65) of the PAs. The MIBI scan did not contribute meaningful information for any of the 65 patients who had positive PTH washout results.

Conclusion: These findings strongly support the use of preoperative dedicated ultrasound as the initial standard procedure. When a PA candidate on ultrasound is found, a PTH washout should be performed. If positive, it could suffice as the sole localization method for MIP surgery. When a PA was identified on ultrasound and confirmed with PTH washout, the MIBI scan did not add more information. Benefits include fewer patient tests, less exposure to ionizing radiation, and reduced healthcare expenses.