Diagnostic Efficacy of UBI Scan in Musculoskeletal Infections

Limited recent studies have demonstrated that 99mTc-UBI scan can be a helpful method in precise diagnosis of infection. In the current study, we aimed to investigate the diagnostic efficacy of 99mTc-UBI scan in detection of musculoskeletal infections. Fifty patients with suspected musculoskeletal infections (painful THA, TKA, implant and nonunion) were enrolled in this study. After injection of 99mTc-Ubiquicidin 29-41, up to 30 minutes, dynamic imaging was performed every 1 minute. Whole body anterior and posterior images were acquired at 60 and 120 min (5 min/frame). A polygonal region of interest (ROI) was drawn manually around the area of increased accumulation of tracer (lesion) and anatomically similar area on the contralateral side (background) and the lesion to background ratio (LBR) was calculated. Then, patients underwent surgical procedures to assess infection by tissue sampling and histopathologic studies as gold standard. The receiver operating characteristics (ROC) analysis was performed to find a cut-off value for LBR and determining the diagnostic efficacy of UBI scan in musculoskeletal infections. Histopathologic studies revealed infection in 38 patients. The mean LBR was significantly higher in infected patients (2.05 ± 0.41 vs. 1.52 ± 0.22; P < 0.001). ROC analysis showed that a cut-off point of 1.74 for LBR will have 94.7% sensitivity, 83.3% specificity and 92% accuracy for diagnosis of musculoskeletal infections. UBI scan is a useful diagnostic tool for evaluation of patients with suspected musculoskeletal infection. However, UBI imaging has some limitations which result in some incorrect diagnoses. It is important to interpret the results of the scan with regard to the clinical findings.