The Sestamibi Scan as a Preoperative Screening Tool

Abstract

Sestamibi scan is generally recognized in the literature to play a role in the imaging of parathyroid adenoma. Most institutions quote sensitivities ranging from 80 to 100 per cent. There is still a question as to whether patients need preoperative localization studies. Preoperative localization can potentially result in less invasive surgery, shorter operative times, decreased hospital stays, and decreased need for re-exploration. Our hypothesis is that the sestamibi scan is a sensitive predictor of parathyroid adenomas. The objectives of this study are to determine the sensitivity of sestamibi scan in detecting parathyroid adenoma, and to determine whether either parathyroid hormone (PTH) level or calcium level is an independent predictor of a positive scan. One hundred patients were retrospectively reviewed at Louisiana State University Health Sciences Center-Shreveport and Louisiana State University Health Sciences Center-Monroe from March 1993 through December 2000. All patients had a preoperative sestamibi scan. This scan was performed using the dual-phase technique in which the parathyroid glands are visualized after washout of tracer from the thyroid. The scan was followed by either a unilateral or bilateral neck dissection. There were 82 female patients and 18 male patients who ranged in age from 23 to 78 years. The median weight of glands with a positive scan was 795 mg. The median weight of glands with a negative scan was 480 mg. This difference was statistically significant (P < 0.04). Overall there were 107 adenomas. Of these 93 had positive scans and 14 had negative scans. This results in a sensitivity of 87 per cent. There were 67 glands that weighed at least 500 mg. Of these 67 glands 61 had positive scans and six had negative scans. This resulted in a sensitivity of 91 per cent. There were 40 glands that weighed less than 500 mg. Of these 40 glands 32 had positive scans and eight had negative scans. This resulted in a sensitivity of 80 per cent. Using multiple linear regression analysis calcium level correlated with the weight of the gland (P < 0.01). Calcium level also correlated with the PTH level (P < 0.01). However, neither the PTH level nor the calcium level correlated with a positive sestamibi scan. Sestamibi scan is a sensitive predictor for parathyroid adenoma greater than 500 mg (91% sensitivity). Even in smaller glands (<500 mg) 80 per cent sensitivity was demonstrated. Although the calcium level correlates with the PTH level neither PTH level nor calcium level is predictive of a positive sestamibi scan.