Technetium-99m-sestamibi Subtraction Scintigraphy Vs. Ultrasonography Combined with a Rapid Parathyroid Hormone Assay in Parathyroid Aspirates in Preoperative Localization of Parathyroid Adenomas and in Directing Surgical Approach

Objective: To determine the sensitivity and positive predictive value (PPV) of subtraction scintigraphy (SS) vs. ultrasonography (US) of the neck combined with rapid intact parathyroid hormone (iPTH) assay in US-guided fine-needle parathyroid aspirates in preoperative localization of parathyroid adenomas and in directing surgical approach.

Design: The results of SS for localization of parathyroid adenoma were determined in 121 patients with primary hyperparathyroidism (pHPT) and compared with findings at surgery and with the results of US alone (in patients without nodular goitre) and US in combination with the iPTH assay in US-guided fine-needle aspirates (FNAs) of suspicious parathyroid lesions (in patients with concomitant nodular goitre).

Patients: All 121 patients had biochemically documented pHPT; all were referred for first-time surgery.

Measurements: SS was performed with 99mTc-sestamibi and 99mTc-pertechnetate. High-resolution US of the neck was performed by a single endocrine surgeon and combined with US-guided FNAs of suspicious parathyroid lesions in all patients with nodular goitre (n = 43).

Results: The sensitivity and PPV of SS were significantly higher in patients without vs. with goitre (89.3% and 95.7%vs. 74.3% and 76.5%, respectively; P < 0.001). The sensitivity and PPV of US were significantly higher in patients without vs. with goitre (96% and 97.3%vs. 67.7% and 71.9%, respectively; P < 0.001). The iPTH assay of US-guided FNAs of suspicious parathyroid lesions in patients with nodular goitre significantly improved both the sensitivity and PPV of US imaging (90.7% and 100%, respectively), allowing for an accurate choice of surgical approach in 118 (97.5%) of 121 patients. SS was more accurate than US alone in detection of ectopic parathyroid adenomas. However, US alone was characterized by a higher sensitivity in detection of small parathyroid adenomas (< 500 mg) at typical sites (P < 0.01).

Conclusions: Both the sensitivity and PPV of SS and US alone are comparable, with significantly less accurate results obtained in patients with goitre. In cases of equivocal results of US and/or in patients with concomitant goitre, an iPTH assay in US-guided FNAs of suspicious parathyroid lesions may be used to establish the nature of the mass, distinguish between parathyroid and nonparathyroid tissue (goitre, lymph nodes) and improve the accuracy of US parathyroid imaging, allowing for successful directing of surgical approach in a majority of patients.