Comparison between Leukoscan® (Sulesomab) and Gallium-67 for the diagnosis of osteomyelitis in the diabetic foot

Objectives: The diagnosis of osteomyelitis in patients with diabetic foot is difficult both clinically and radiologically. An early diagnosis is crucial to optimize therapeutic strategy. Among the diagnostic methods currently used, scintigraphy with ex-vivo labelled white blood cells is the gold standard, but cannot be performed in all centers; therefore (67)Gallium citrate (Ga-67) imaging in combination with a bone scintigraphy is still widely used. Method: The results of imaging 24 diabetic patients with 31 suspected osteomyelitic lesions using the antigranulocyte Fab' fragment (Sulesomab or LeukoScan (R) or immunoscintigraphy) were prospectively compared with results from the bone scan coupled with Ga-67. The diagnosis of osteomyelitis was confirmed by either biopsy or follow-up, radiological imaging and clinical outcome. Results and conclusion: Sulesomab correctly identified 12 of 18 osteomyelitic lesions while Ga-67 was able to detect only 8 of 18. Therefore the sensitivity is 67% for Sulesomab and 44% for Ga-67. Among the 13 non-osteomyelitic lesions imaging with Sulesomab was able to rule out infection in 11 cases and Ga-67 in 10 cases. The specificity is therefore 85% for Sulesomab and 77% for 17 Ga-67 Image interpretation for Sulesomab in this group of patients is occasionally suboptimal when imaging is performed at 3 hours post injection. High vascular background in the early images may obscure infection especially in small bones. Practically, scintigraphy with Sulesomab is fast and simple due to ease of labeling, no ex-vivo handling of blood, low radiation and provides rapid diagnosis. The diagnosis of osteomyelitis obtained by the antibody fragment scintigraphy influences the management (guided biopsy) and therapy. In several patients, imaging with Sulesomab was able to rule out osteomyelitis, helping to avoid useless antibiotic therapy and its associated side effects.