Ultrasonography (US) and Tc-99m sestamibi scintigraphy (SS) are usually performed as preoperative imaging modalities for patients with sporadic primary hyperparathyroidism (SPHP). Fine-needle aspiration (FNA) under US guidance for parathyroid hormone (PH) assay can enhance the diagnostic accuracy of US. The main aim of the present study was to compare positive predictive values between US-FNA and SS. The secondary aim was to draw up a decision-tree for FNA and SS.

The single-center retrospective study included patients with previously non-operated SPHP. They underwent US-guided FNA, PET-CT SS, and 18 F-choline scintigraphy if the first two methods were inconclusive. PH washout level was considered pathological when greater than the serum PH level. Postoperative histology data were correlated to imaging data.

In total, 117 patients were included, with a mean age of 64 years (range, 26–89 years). A single adenoma was identified on pathology in 101 patients (89%). FNA findings were pathologic for 64 patients (55%), with a mean PH level of 2,604ng/L [range, 585–9,074ng/L], higher than the serum level of 179ng/L [range, 60–1,000ng/L]. US-guided FNA showed sensitivity, specificity, and positive and negative predictive values (PPV, NPV) of respectively 72%, 92%, 99% and 28%, compared to 89%, 42%, 93% and 32% for SS. The rate of error in locating the parathyroid gland was 8% for US-guided FNA versus 12% for SS. Comparison of the two methods showed better sensitivity for SS (P=0.0052) and better specificity for FNA (P=0.0143), with no significant difference in PPV or NPV. 18 F-choline scintigraphy detected the hyperfunctioning parathyroid in 11 out of the 15 patients.

PPV did not significantly differ between FNA and SS. US-guided FNA performed by an experienced operator could be a simple first-line method for more than 50% of patients with non-operated SPHP, with 99% PPV. In case of negative or doubtful FNA findings, SS can be performed in second line.