Effective factors on the sensitivity of preoperative sestamibi scanning for primary hyperparathyroidism

Preoperative accurate localization of enlarged adenoma (s) in primary hyperparathyroidism (PHPT) is a vital necessity. Technetium 99m sestamibi scanning is commonly used with reported acceptable sensitivities; however, false negative scan studies remain a problem. Determining effective factors on the sensitivity of the scan might improve the diagnostic value of the study by selecting the correct candidates.

Patients with PHPT indicated for parathyroidectomy from June 2008 to June 2013 who had positive ultrasonographic findings for single adenoma were included in the study. All patients underwent 99m-Tc MIBI scintigraphy before the surgery. Postoperative histopathology results were used as gold standard. The effect of patients' age, gender, preoperative serum PTH level, volume of the gland and having cystic components in the adenoma on the results of the scan were investigated.

A total of 70 patients (mean age: 47.76 ± 11.80; 87.1% (n = 61), female) were included. Mean PTH level was 508.01 ± 360.47 pg/mL and mean volume of the parathyroid gland was 1.94 ± 1.52 cc. 27.1% (n = 19) of the adenomas had a cystic component in the ultrasonography. Sensitivity of MIBI scan was 70%. Mean PTH level was 588.86 ± 372.95 pg/mL in positive MIBI scans compared with 319.38 ± 247.19 pg/mL in negative scans. Sensitivity of the scan increased significantly with higher levels of serum PTH level. Age and gender of the patients as well as volume of the gland were not related with scan results. Adenomas with cystic component had significantly higher volume and lower serum PTH levels; and although false negative studies were more common than solid adenomas, the difference was not statistically significant.

Sensitivity of the MIBI scan reduces significantly in lower levels of preoperative serum PTH. This should be particularly considered in adenomas with cystic components. Concomitant use of Ultrasonography can increase the accuracy of preoperative localization in such cases.