Serum inflammatory markers for periprosthetic knee infection in obese versus non-obese patients

Accurate diagnosis of periprosthetic joint infection (PJI) is challenging. Most infection diagnosis criteria define elevated serum C-reactive protein (CRP) as >1.0mg/dL and erythrocyte sedimentation rate (ESR) as >30mm/hour. Obesity has been reported as a pro-inflammatory state with elevated baseline CRP values. We hypothesized that higher cut-off values would be more accurate to diagnose PJI in obese patients due to their elevated baseline CRP. BMI, serum inflammatory markers, and synovial fluid were collected for 102 revision total knee arthroplasty patients, and analyzed for the highest area under the curve. We found a CRP of 3.6mg/dL was more accurate to diagnose PJI in obese patients versus traditional values. Clinicians should be judicious and use additional criteria when diagnosing PJI in obese patients.