Re-evaluating the potentials and limitations of (99m)Tc-aprotinin scintigraphy for amyloid imaging.

The definitive diagnosis of amyloidosis is made histologically with Congo red stain. Noninvasive imaging techniques for amyloidosis are beneficial for early and definite diagnosis of amyloid deposition in the body. (99m)Tc-aprotinin has the benefit of detecting amyloid deposits mainly in the heart, but it can also detect a wide range of lesions in other locations. The usefulness and limitations of (99m)Tc-Aprotinin scintigraphy for amyloid imaging were re-evaluated based on results from 25 patients (15 men and 10 women; median age, 62.9 y; range, 34-83 y). In addition, other nuclear tracers for imaging amyloidosis are discussed. Of the 25 patients with suspected amyloidosis, 19 patients were proven to have amyloid deposits by histopathological diagnosis. Major (99m)Tc-aprotinin positive sites were confirmed in the myocardium, thyroid, large joints, vertebrae, colon, and lungs. If (99m)Tc-Aprotinin images showed positive findings, the sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of existing amyloid deposits were 94.7, 33.3, 81.8, and 66.7%, respectively. For analysis based on biopsy region, the sensitivity, specificity, PPV, and NPV of existing amyloid deposition were 30.6, 82.6, 73.3, and 43.2%, respectively. (99m)Tc-Aprotinin has a high potential for diagnosis of amyloid deposition in body; however, due to its physiological uptake, its potential is limited for detection of amyloid deposits in the liver, kidney, and spleen.