Synovial fluid calprotectin quantitative rapid diagnostic biomarker for risk stratification of periprosthetic joint infections.

Purpose: Diagnosing periprosthetic joint infections (PJI) are challenging and may be hampered by the presence of other causes of local inflammation. Recently, several synovial biomarkers have been introduced into the algorithm for the diagnosis of a PJI. Calprotectin is a protein that is present in the cytoplasm of neutrophils, is released upon neutrophil activation, and exhibits antimicrobial activity. The purpose of this study is to demonstrate calprotectin as a promising biomarker for the diagnosis of PJIs.

Methods: This retrospective single-center study (Dec 2020-Nov 2023) included 52 patients undergoing revision arthroplasty on the grounds of confirmed or suspected infection as per the criteria of the Infectious Diseases Society of America (IDSA) for PIJs. Synovial fluid calprotectin was measured intraoperatively using a quantitative lateral flow assay. Diagnostic accuracy was evaluated against tissue culture using ROC analysis, Cohen's kappa, sensitivity, and specificity.

Results: Revision procedures included hip (44%), knee (25%), and shoulder (8%) arthroplasties. Calprotectin testing indicated high infection risk in 40.4% of patients, while periprosthetic tissue cultures were positive in 53.8%. Agreement between the tests was good (Cohen's kappa = 0.735). Calprotectin testing showed a sensitivity of 75%, specificity of 100%, positive predictive value of 100%, negative predictive value of 78%, and an area under the receiver operating characteristic curve of 0.875.

Conclusion: The study highlights the diagnostic value of synovial fluid calprotectin as a diagnostic biomarker with high sensitivity and specificity in the diagnosis of PJI.