Utility of 99mTc dextran scintigraphy in diabetic patients with suspected osteomyelitis of the foot.

PURPOSE Osteomyelitis of the foot is a frequent complication of diabetes mellitus and its diagnosis is often difficult. The goal of this study was to demonstrate the utility of 99mTc dextran scintigraphy in suspected diabetic foot infections. MATERIALS AND METHODS Twenty-six patients (20 males, 6 females, age range 18-80 years) with diabetes mellitus who had a total of 36 foot ulcers or necrosis were studied. All the patients underwent both three phase bone scan and 99mTc dextran scintigraphy. Final diagnosis was based upon either pathologic examination or clinical follow-up at least four months. RESULTS On bone scan increased uptake was seen in 55 sites, and among these there were 11 lesions of proven osteomyelitis. There were 11 true-positive, 0 false negative, 0 true negative and 44 false positive results for bone scan. The sensitivity, specificity and accuracy of bone scan were 100%, 0% and 20%, respectively. With regard to 99mTc dextran scan, nine lesions produced true-positive results with two lesions indicating false negatives resulting in a sensitivity of 82%. Thirty-six true negative and eight false positive results produced a specificity of 82%, and an accuracy 82% from 99mTc dextran studies was obtained. Eight false-positive results were possibly due to neuroarthropathy, pressure points and deep penetrating ulcers. A patient with one false-negative result had angiopathy while other had neither neuropathy nor angiopathy. CONCLUSIONS According to these results, 99mTc dextran scintigraphy seems to be a sensitive and specific diagnostic method, and because of its advantages over other radiopharmaceuticals (shorter preparation time, highly stability in vivo/in vitro, early diagnostic imaging and low cost), it may be a radiopharmaceutical of choice for diagnosing in diabetic foot infections.