Preoperative localization in primary hyperparathyroidism: a stepwise approach integrating PTH-FNA washout and second-line 18F-choline PET/CT.

OBJECTIVE: Accurate preoperative localization of parathyroid adenomas is essential for the success of minimally invasive parathyroidectomy. This study evaluated the detection rate of parathyroid hormone assay on fine-needle aspiration washout and in conventional and advanced imaging modalities modeling a hypothetical stepwise diagnostic approach for primary hyperparathyroidism. METHODS: We conducted a retrospective single-center study including 32 patients with primary hyperparathyroidism who underwent minimally invasive parathyroidectomy and preoperative parathyroid hormone assay on fine-needle aspiration washout. We used the PTH-FNA washout to serum PTH ratio as the cutoff: a value greater than 1 was considered indicative of positive localization, while a value equal to or less than 1 was considered negative. Preoperative localization procedures included ultrasonography, MIBI-Scan, and 18F-choline PET/CT. Results were compared with postoperative histology and biochemical outcome. RESULTS: Parathyroid hormone assay on fine-needle aspiration washout was positive in 20 of 32 patients (62.5%, 95% CI 45.3-77.1%). Among washout-positive patients, 7 of 20 (35.0%) underwent surgery based on ultrasonography and washout findings alone, with histological confirmation of parathyroid adenoma in all cases. In the washout-positive subgroup in whom MIBI-Scan was also performed, scintigraphy was diagnostic in 7 of 13 cases (53.8%). In washout-negative patients, scintigraphy localized the lesion in 6 of 12 cases (50.0%). In patients with non-localizing washout and scintigraphy findings, 18F-choline PET/CT identified the lesion in all evaluated cases. In this retrospective series, a stepwise strategy based on ultrasonography combined with needle-aspiration washout as the first-line localization, followed by 18F-choline PET/CT in washout-negative cases, could have potentially avoided MIBI-scans in 25 out of 32 patients (78.1%; 95% CI 61.2-89.0%). CONCLUSION: This retrospective, single-center, post-hoc reconstructed cohort study might suggest a stepwise approach for preoperative localization of parathyroid adenoma based on parathyroid hormone assay on fine-needle aspiration washout combined with ultrasonography as a useful first-line diagnostic technique and reserving 18F-choline PET/CT for non-localizing cases. It may reduce the use of additional imaging and radiation exposure. Larger prospective studies are needed to confirm these findings.