Neopterin, Interleukin-6, Procalcitonin, C-reactive protein and PET-CT staining as markers in infected total knee prosthesis, a retrospective analysis
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Diagnosis in prosthetic joint infections is challenging as symptoms are variable, and currently most of the diagnostic tests are non-specific. Normal inflammatory reactions after orthopedic prosthetic surgery may generate false positives, as these tests have high sensitivity, but low specificity. Thus, specific tests, as alpha defensin, are needed to distinguish bacterial infections from reactions to surgical trauma. The aim of this study was to determine the sensitivity and specificity of several diagnostic tools for detecting bacterial infection in prostheses. Between April 2010 and December 2012, we analyzed white blood cell count, erythrocyte sedimentation rate, C-reactive protein, neopterin, interleukin-6, and procalcitonin in 45 patients with prosthetic infection confirmed by positive cultures of joint aspirate and deep tissue biopsy. In addition, these patients underwent PET-CT imaging, in accordance with infection protocols in place at our clinic. The suitability and diagnostic power of these tests were assessed by using Shapiro-Wilk test, Mann-Whitney U test, and ROC curve analysis, and by comparing to 40 age- and gender-matched volunteers who underwent unilateral total knee prosthesis with normal serum indices and without known diseases. Significant differences were observed between infected patients and control volunteers (p < 0.05) for all parameters examined. Highest sensitivity (99%) and specificity (98%) were achieved using a combination of interleukin-6 and C-reactive protein. However, PET-CT imaging had diagnostic accuracy of 93.3%. A combination of interleukin-6 and C-reactive protein also enables accurate diagnosis. PET-CT may be an important imaging modality for detecting prosthesis infection. But, these markers were found neither sensitive nor specific in the diagnosis of periprosthetic infection as alpha defensin.