Diabetic foot infections: scintigraphic evaluation with 99Tcm-labelled anti-granulocyte antibodies

Thirty-eight lesions found by physical and/or radiological examination in 25 patients with long-term diabetes mellitus were studied in order to evaluate the clinical utility of immunoscintigraphy using 99Tcm-labelled anti-granulocyte monoclonal antibodies (MAb BW 250/183) for the diagnosis of infectious pathology in diabetic foot. All the patients underwent three-phase bone scintigraphy with 740 MBq 99Tcm-methylene disphosphonate. Immunoscintigraphy was performed 4 and 24 h after administration of 500 MBq of the labelled antibody by planar selective views. Uptake intensity was scored 0 to 4 (0 = normal, 1 = mildly increased, 2 = moderately increased, 3 = intense, 4 = very intense) when compared with adjacent or contralateral uninvolved bone marrow and soft tissue. Several projections were performed and anatomical references of bone scan were used to determine whether the lesion involved the bone or soft tissue. Definitive diagnoses were 15 osteomyelitis, 14 soft tissue lesions (nine cellulitis and five noninfected ischaemic or trophic wounds), and nine degenerative bone disease. 99Tcm-granulocyte scintigraphy showed increased uptake in seven soft tissue lesions, in four of which exclusively soft tissue involvement was demonstrated by scintigraphy. Only one false negative scintigraphic finding was observed (chronic osteomyelitis). No abnormal anti-granulocyte antibody uptake was observed in degenerative lesions. Based on our observations, immunoscintigraphy with 99Tcm-MAb BW250/183 has a sensitivity of 93% in the diagnosis of osteomyelitis involving diabetic patients' feet. Although it is feasible to distinguish exclusive soft tissue involvement, this is still the main cause of misdiagnosis in current clinical practice.