Evaluation of 99mTc-Ubiquicidin 29–41 Scintigraphy in Differentiation of Bacterial Infection from Sterile Inflammation in Diabetic Foot

Introduction: Ubiquicidin (UBI) 29–41 is a synthetic antimicrobial peptide that binds with the microbial cell membrane at the location of infection. This study was conducted to evaluate its probable efficacy as an infectionimaging agent with potential to differentiate bacterial infection from sterile inflammation in humans. Methods: Fifteen diabetic foot patients (10 males and 5 females) with suspected bacterial infection, prior to starting antibiotic treatment, were selected for this study. First a routine three phase bone scan and later a 99mTc-UBI scan was performed for all the patients. 555-740 MBq of 99mTc-UBI was injected intravenously. A 10 minute dynamic study was followed by spot views of the suspected region of infection and corresponding normal areas (liver and kidneys) at 60 and 120 min. Whole-body anterior and posterior images were also acquired. To interpret the studies as positive or negative, visual score (0 –3) was used, with scores of 0 (minimal or no uptake; equivalent to soft tissue) and 1 (mild; less uptake than in liver) being considered negative and scores of 2 (moderate; uptake equal to or greater than that in liver) and 3 (intense uptake equal to or greater than that in kidneys) being considered positive. Results: Of 15 studies performed with 99mTc-UBI, all had positive bacterial cultures. The result of bone scan was positive for osteomyelitis in 12 patients (80%). 99mTc-UBI Scintigraphy was positive in 6 patients, but negative in nine. The sensitivity of 99mTc-UBI for detection of infection was therefore 40%. From 12 patients who had positive bone scans, only 6 had a positive 99mTc-UBI (50%) indicating the sensitivity of 50% for 99mTc-UBI in osteomyelitis cases. 99mTc-UBI was not positive in any patient who had evidence of soft tissue infection in the bone scan. Conclusion: Although 99mTc-UBI 29–41 was well tolerated by all the patients without any side effects, considering low sensitivity of this agent, this radiopharmaceutical is not of great value for diabetic foot infection diagnosis.