SESTAMIBI VERSUS THALLIUM SUBTRACTION SCINTIGRAPHY IN PARATHYROID LOCALIZATION - A PROSPECTIVE COMPARATIVE-STUDY IN PATIENTS WITH PREDOMINANTLY MILD PRIMARY HYPERPARATHYROIDISM

Background. Technetium 99m sestamibi was recently introduced for the p reoperative localization of abnormal parathyroid glands in patients wi th primary hyperparathyroidism with promising results. However, the se nsitivity of sestamibi and thallium to detect abnormal parathyroid gla nds is partly dependent on the gland size. In this study we compared t he sensitivity of sestamibi subtraction scintigraphy with thallium sub traction scintigraphy in patients with predominantly mild increase in serum calcium level. Methods. Thirty-nine patients with primary hyperp arathyroidism were included. The mean (+/-SD) serum level of calcium w as 2.75 +/- 0.17 mmol/L. In 28 (72%) of the patients the serum level o f calcium was less than 2.85 mmol/L. These patients were classified as having mild abnormalities in serum calcium. All patients were investi gated before operation with both sestamibi and thallium subtraction sc intigraphy. Results. In two patients autonomous thyroid adenomas precl uded subtraction scintigraphy. Sestamibi subtraction scintigraphy corr ectly localized 31 (86%) of 36 parathyroid adenomas compared with only 17 (47%) of 36 by thallium subtraction scintigraphy (p < 0.001). Ther e was one false- positive result in the sestamibi group because of a t hyroid adenoma, and two of the scans were negative. Both the sestamibi and the thallium subtraction scintigraphy localized one single enlarg ed gland in all three patients with multiple gland involvement. In no case was multiglandular disease predicted. Conclusions. Sestamibi subt raction scintigraphy is superior to thallium subtraction scintigraphy and has a high sensitivity to localize a solitary parathyroid adenoma in patients with mild increase in serum calcium level. The sensitivity decreases in patients with multiglandular parathyroid disease and con comitant thyroid nodular abnormalities.