Comparison of pertechnetate and radioiodine thyroid scintiscans in thyroid disease

In a retrospective study, thyroid scintiscan with technetium-99m-pertechnetate at 30 minutes was compared with the iodine-131 scan at 24 hours in 273 patients with various thyroid diseases. The pertechnetate scan showed normal or diffusely enlarged thyroid glands in 64 patients, cold nodules in 36, and hot or warm nodules in 173. The radioiodine and pertechnetate scintiscans were concordant in all patients without nodules and in those with cold nodules. Minor discrepancies were observed in 24 patients with hot or warm nodules. Only 2 patients, both euthyroid, showed major discrepancies in which nodules appeared hot with pertechnetate and cold with radioiodine. Sequential scintiscans with radioiodine performed in both of these patients, and a perchlorate test performed in one, demonstrated organification defects in the nodules. The data indicate that there is a high correlation between the results of scintiscans using the two tracers; discrepancies in results with the two imaging techniques were rare.