Noninvasive diagnosis of gastroesophageal inflammation using dipyridamole thallium 201 scanning

BACKGROUND: GERD, defined as symptoms or tissue damage resulting from the reflux of gastric contents, is a common medical problem. Approximately 50% of patients with GERD will have evidence of esophagitis on endoscopy. Radiopharmaceuticals, (GA 67, Tc 99m pertechnetate), have been used to diagnosis GI pathology in a noninvasive manner. We hypothesized that esophagitis and gastric erosions seen endoscopically could also be detected using dipyridamole thallium 201 (DT 201) scanning, and if true this could serve as a useful, noninvasive screening test for esophagitis, etc.. METHODS: A pilot study was undertaken in which 12 patients underwent EGDs for symptoms of GERD or dyspepsia. A diagnosis of esophagitis required the presence of erosions and gastric erosions were defined as discreet mucosal breaks measuring 1 mm or more. DT 201 scanning was performed the following day on all 12 patients. A standard dose of dipyridamole (0.56mg/kg) was infused followed by a 3 mCu dose of thallium 201. Initial, stress images and reinjection (1 mCu) resting images were obtained using a gamma camera. Images were read by a cardiologist who was blinded to the EGD results. Thallium uptake was graded on a 0 to 3+ scale using the liver uptake as the internal comparative standard (2+ = uptake equal to the liver). Abnormal thallium uptake was defined as 2+ or greater in the area of the esophagus or stomach. RESULTS: Seven females and 5 males (mean age of 41 years old; range 25-60) were studied. Eight patients were on histamine-2 receptor antagonists and none were on proton pump inhibitors, or promotility agents. Five patients had endoscopic esophagitis with 4 of these 5 having positive thallium scans Seven patients had no evidence of erosive esophagitis. yet 3 of 7 had positive thallium scans, Sens., spec., pos. and neg. predictive values for DT 201 to detect esophagitis were 80%, 57%, 57%, and 80%. With regard to the stomach. 3 patients had gastric erosions and had positive thallium scans. Six of the remaining 9 patients without gastric erosions had positive thallium scans. Sens., spec., pos. and neg. predictive value for DT 201 to detect gastric erosions were 100%, 33%, 33%, and 100%. CONCLUSIONS: DT 201 has poor predictive value for identifying esophagitis or clinically significant gastric pathology, therefore is not a useful noninvasive screening test for these diseases. Additionally, the cost of radiopharmaceuticals requires that sens/spec equal that of endoscopy in order for it to be clinically valuable.