Evaluation of Infections of the Locomotor System with Indium-111-Labeled Human IgG Scintigraphy

Indium-111-labeled human nonspecific immunoglobin G (111In-IgG) is one of the newer agents suggested for scintigraphic evaluation of infection and inflammation. In this study, the utility of this agent was studied in routine clinical practice. A dose of 75 MBq 111In labeled to 2 mg IgG (MacroScint) was administered intravenously in 226 patients with 232 possible foci of infection or inflammation. Imaging was performed 4, 24 and 48 hr postinjection. The results were verified by culture, obtained either surgically (42%) or via puncture (19%) and long-term clinical and roentgenological follow-up (39%). Follow-up data were used in patients of whom the vast majority had a negative work-up, including negative 111In-IgG scintigraphy. All infected total hip (THA) and total knee arthroplasties, focal osteomyelitis, diabetic foot infections, septic arthritis and soft-tissue infections were detected (61 foci). Only one patient with early, low-grade spondylodiscitis was false negative with 111In-IgG. Since 111In-IgG scintigraphy does not discriminate between infectious and sterile inflammation, careful interpretation is necessary in cementless THA up to 1 yr after insertion, uptake only around the neck of the femoral component of a THA, recent fractures and pseudarthrosis, in which uptake may be caused by sterile inflammation and not by infection (specificity for inflammation 100%, specificity for infection of 77%). Indium-111-IgG scintigraphy is a very sensitive tool for detection of infectious bone and joint disease. Moreover, when uptake patterns of 111In-IgG, which are characteristic for sterile inflammation, are excluded, infection can be ruled out with a high degree of certainty.