Comparison of 99mTc ciprofloxacin, 99mTc white blood cell and three-phase bone imaging in the diagnosis of hip prosthesis infections: improved diagnostic accuracy with extended imaging time.

The purpose of this study was to compare the utility of 99mTc labelled ciprofloxacin (Infecton) imaging with the 99mTc white blood cell and three-phase bone imaging procedures for identifying hip prosthesis infection. We studied 30 symptomatic patients in whom infection was confirmed in eight and excluded in 22 cases based on clinical and microbiological findings. 99mTc ciprofloxacin images were obtained at 1, 4 and 24 h after the injection of the tracer, and the data were compared to those obtained from 99mTc leukocyte and three-phase bone imaging. The 99mTc ciprofloxacin imaging correctly identified all true infections. In 13 (59%) of the non-infected patients, non-specific uptake of 99mTc ciprofloxacin was found in the 1-h and 4-h images, which disappeared, however, in the 24-h images. When the early and late 99mTc ciprofloxacin images were compared, the specificity was found to improve from 41% to 95%, positive predictive value from 38% to 89%, and the diagnostic accuracy from 57% to 97%. The accuracy of the conventional 99mTc leukocyte imaging was 90%. Dynamic bone imaging also yielded abnormal findings in all the infected patients although also in 23% of the non-infected patients. Current data indicate that 99mTc ciprofloxacin is a useful method for confirming hip prosthesis infection. The diagnostic efficiency of this method is improved when the imaging time is extended to 24 h post-injection of the tracer.