Cell-free Deoxyribonucleic Acid: A Potential Biomarker of Chronic Periprosthetic Knee Joint Infection.

BACKGROUND: The correct diagnosis of a chronic periprosthetic joint infection (PJI) is a major challenge in clinical practice, with the "gold standard" for diagnosis yet to be established. Synovial fluid analysis has been proven to be a useful tool for that purpose. Cell-free DNA (cf-DNA) levels have been shown to be increased in several conditions such as cancer, trauma, and sepsis. Therefore, this study was designed to evaluate the potential of synovial fluid cf-DNA quantification for the diagnosis of chronic periprosthetic infections following total knee arthroplasty. METHODS: A prospective study with patients undergoing total knee arthroplasty revision surgery for any indication was performed. PJI diagnosis was defined according to the Second International Consensus Meeting on Musculoskeletal Infection (2018) criteria. The study cohort consisted of 26 patients classified as infected and 40 as noninfected. Synovial fluid cf-DNA direct quantification by fluorescent staining was made. Sensitivity, specificity, and receiver operating characteristic curve were calculated. RESULTS: The cf-DNA levels were significantly higher in patients who had PJIs (122.5 ± 57.2 versus 4.6 ± 2.8 ng/µL, P < .0001). With a cutoff of 15 ng/µL, the area under the receiver operating characteristic, sensitivity, and specificity of cf-DNA were 0.978, 96.2%, and 100%, respectively. CONCLUSION: The present study has shown that cf-DNA is increased in synovial fluid of patients who have chronic PJIs. It is a promising biomarker for knee PJI diagnosis and further studies are needed to confirm its utility.