Diagnostic value of routine pre-operative investigations used in combination in the diagnosis of periprosthetic joint infection

Abstract

The primary aim of this study was to assess the diagnostic accuracy of joint aspiration culture, serum C-reactive protein (CRP) and serum erythrocyte sedimentation rate (ESR), individually, and in combination for the diagnosis of periprosthetic joint infection (PJI). A consecutive patient series with pre-operative inflammatory marker levels, an aspiration culture of either hip or knee arthroplasty and intra-operative culture samples from subsequent revision surgery was compiled. This retrospective patient cohort analysis included 128 aspiration. The data were analysed to compare pre-operative aspiration cultures, serum ESR and CRP levels to the chosen gold standard for PJI diagnosis of intra-operative culture samples. A diagnostic algorithm was created using the above tests combined with clinical suspicion index. The values that had the highest sensitivity and specificity of predicting PJI were >5 for CRP and >16 for ESR. CRP used individually had the highest sensitivity and negative predictive value (NPV) of any test (75.0% and 75.9%, respectively). ESR + aspirate had the highest specificity and positive predictive value (PPV), of 100% for both. Using all three tests together the specificity and PPV were higher than the test individual values (95.3% and 85.0% respectively). Based on subgroup analyses the combination of ESR or CRP plus joint aspiration has superior PPV compared to individual tests. ESR and CRP had the highest NPV when used in isolation. An algorithm has been developed to guide clinical diagnosis.