Comparison of Tc-99m Pertechnetate Thyroid Uptake Rates by Gamma Probe and Gamma Camera Methods for Differentiating Graves’ Disease and Thyroiditis

Although technetium-99m ( 99m Tc) pertechnetate thyroid uptake rate can be measured by gamma camera with scintigraphy as well as by gamma probe, the normal reference range known as quite different between them. This study was performed to compare their diagnostic accuracy for evaluating patients with hyperthyroidism. We retrospectively reviewed consecutive 371 patients (euthyroid 89, Graves 167, and thyroiditis 115) who had simultaneously measured data of thyroid uptake rates by both gamma probe and camera methods in our hospital from November 2019 to June 2020. The reference ranges in euthyroid patients were 2.0-4.7% and 0.3–1.9% for probe and camera methods, respectively. For differentiating Graves’ disease and thyroiditis, the area under the curve of the camera method was significantly greater than that of the probe method (0.988 vs 0.975, p  = 0.030) on receiver operating characteristic curve analysis. With a cutoff value of 0.7%, the sensitivity and specificity for the camera method were 93.4% and 94.8%, respectively. With a cutoff value of 3.0%, those for the probe method were 92.2% and 91.3%, respectively. In conclusion, 99m Tc pertechnetate thyroid uptake rate measured by the camera method with scintigraphy had higher diagnostic accuracy than the probe method for evaluating patients with hyperthyroidism.