Background: The aim of this study was to assess the value of a technetium ((99m)Tc)-polyclonal antibody to detect acute appendicitis in patients with intermediate probability of appendicitis.
Methods: A total of 40 patients with mean age of 24.6 ± 6.9 years with intermediate probability of appendicitis according to the Alvarado scoring system (score 5 or 6) were studied. After intravenous injection of 740 MBq of (99m)Tc-immunoglobulin G (IgG), a flow and blood pool image was obtained followed by two planar images and single photon emission tomography (SPECT) scan from the lower abdominal and pelvic regions. The images were subjected to visual and quantitative analysis. Patients were followed clinically, and the surgeon decided to operate on or observe the patient depending on the clinical findings. The pathology results were considered the gold standard if patients underwent an operation. If patients improved without surgery, it was considered negative for appendicitis.
Results: Altogether, 31 patients were operated on, and 21 patients had acute appendicitis. Nine patients were discharged from hospital and had no symptoms during follow-up. The sensitivity of the planar images for diagnosing appendicitis was 19-24% and specificity was 100%. The sensitivity of SPECT for diagnosis of appendicitis was 62%, the specificity was 68%, and the negative predictive value (NPV) was 62%. Quantitative analysis showed that using a cutoff of >1.2 for the mean right-to-left count per voxel ratio, the sensitivity of the test for detection of appendicitis was 54%, and the specificity was 86%.
Conclusions: (99m)Tc-polyclonal IgG scanning has low sensitivity and moderate NPV for detecting appendicitis. Therefore, it is not a suitable tracer for excluding appendicitis.