A new classification of positive sestamibi and ultrasound scans in parathyroid localization

Ultrasound (US) and sestamibi (MIBI) are traditionally considered positive or negative. The purpose of this study was to define and test a new scoring system for MIBI and US and to determine whether this can improve their accuracy for primary hyperparathyroidism.

This is a prospective study of 200 consecutive patients with primary hyperparathyroidism who had a single uptake on MIBI scans before bilateral neck exploration at a tertiary academic center between 2007 and 2008. These patients also had surgeon-performed neck US in the office, which was scored as "typical" or "atypical" based on how characteristic the image resembled a parathyroid gland. The MIBI uptake was scored by the nuclear medicine specialist as "weak," "moderate," or "strong" compared with the signal intensity of the thyroid. US and MIBI scoring was done preoperatively and their findings were compared with operative data.

Of 200 patients, 71 % had a single adenoma, 12 % had double adenomas, and 17 % had four-gland hyperplasia. A weak, moderate, and strong signal on MIBI had an accuracy of 23, 47, and 72 %, respectively, in demonstrating single-gland disease. An atypical versus typical US appearance was accurate in 55 and 74 % of the time, in identifying single-gland disease.

An appraisal of US and MIBI positivity in relation to image characteristics affects the reliability of both studies. This information should be kept in mind when selecting patients for focal neck exploration.