Serum erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) are commonly used for the diagnosis of persistence of infection after the first stage of 2-stage revision arthroplasty for periprosthetic joint infection (PJI). As both ESR and CRP are markers of systemic inflammation, the utility of these tests to monitor infection clearance in patients with inflammatory arthritis is unclear.
From 2001 to 2016, 44 two-stage revision total hip or knee arthroplasties in patients with an inflammatory arthritis diagnosed by a rheumatologist were identified. Persistence of infection at the time of planned second stage was defined as satisfying the Musculoskeletal Infection Society criteria for PJI (14 infected, 30 noninfected). ESR and CRP values were compared between the stages using nonparametric tests. Receiver operating characteristic analysis was performed to obtain the diagnostic parameters.
ESR and CRP decreased between the stages in the noninfected group (ESR: mean decrease = 31.6 mm/h [19.2-44.0], P < .001; CRP: mean decrease = 5.2 mg/dL [2.1-8.2], P < .001), but remained elevated in the infected group (ESR: mean decrease = 7.7 [−23.1 to 36.6], P = .572; CRP: mean decrease = 1.5 [−2.2 to 5.1], P = .258). Optimal thresholds for persistent infection were 29.5 mm/h and 2.8 mg/dL, respectively, for ESR and CRP. The sensitivity and specificity at the optimal thresholds were 64% and 77% for ESR, and 64% and 90% for CRP.
ESR and CRP responded to the treatment of PJI in patients with inflammatory arthritis and had reasonably high specificities with moderate sensitivities. ESR and CRP appear to be useful tools in diagnosing persistent infection even in patients with inflammatory arthritis.