Value of leukocyte scintigraphy in suspected implant infection in patients with rheumatoid arthritis

When infection of implants is suspected, optimal management requires accurate confirmation or exclusion of infection. However, in spite of demonstrative clinical signs cultures of smears or chemical parameters of inflammation frequently are ambiguous. Scintigraphy with indium-labeled white blood cells (WBC) has been reported to be sensitive and specific in the diagnosis of low-grade sepsis of the musculoskeletal system. Twenty-eight patients with possible infection were prospectively studied. Infection was suspected in 19 cases with total hip joint prosthesis, 14 cases with knee joint prosthesis and 1 case with shoulder joint prosthesis. All of them underwent scanning with indium-111-labeled WBC and subsequently underwent surgery. At surgery infections were determined by means of culture or histologic results. When correlated with culture and histologic results sensitivity of 111-indium-WBC imaging was 89 %, with a specifity of 67 % and a predictive accuracy of 77 %. In patients with rheumatoid arthritis, however, predictive accuracy of 111-indium-labeled WBC imaging was higher than with standard diagnostic methods. The difference was statistically significant (P < 0.05, chi(2)-test). In the patients examined as a whole, predictive accuracy of 111-indium-labeled WBC imaging does not differ from that of standard diagnostic methods. That is why expensive and time-consuming 111-indium-WBC imaging is not justified generally in diagnosis of infection of implants. 111-Indium-WBC imaging is well suit ed to supplement standard diagnostic methods in patients with rheumatoid arthritis.