Predictors of an accurate preoperative sestamibi scan for single-gland parathyroid adenomas

Objective: To investigate why some patients with single parathyroid adenomas have negative preoperative sestamibi scans. Design: Retrospective review. Setting: Tertiary care center. Patients: Twenty-one patients with false-negative (FN) scans were compared with 22 patients with truepositive (TP) scans. All patients had single parathyroid adenomas. Interventions: Neck exploration and removal of parathyroid adenomas. Main Outcome Measures: Age; sex; preoperative serum calcium and parathyroid hormone levels; gland weight; location; and pathologic features. Results: There was no significant difference in age or preoperative serum calcium or parathyroid hormone levels. Gland weight was greater in the TP group compared with the FN group (mean±SD, 1336±1603 mg vs 475±365 mg; P=.04); 13 (62%) of the 21 glands in the FN group were located in the upper position, compared with 6 (27%) of the 22 glands in the TP group (P=.03). Ten of the 22 glands in the TP group consisted predominantly of oxyphil cells, compared with 2 of the 21 glands in the FN group (P=.02). A multivariate logistic regression model yielded the following factors that predicted an accurate scan: higher percentage of oxyphil cells (P = .03), heavier gland (P = .03), female sex (P = .04), and gland location in the lower position (P=.04). Conclusions: Smaller-volume parathyroid adenomas and those in the upper position are less likely to be localized with sestamibi scans. A TP scan correlates with oxyphil cell predominance, supporting a role for the mitochondrial-rich cell in sestamibi uptake and retention.