Abstract
Introduction
Serum erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP), and synovial fluid white blood cell (WBC) count and differential are effective in diagnosing periprosthetic joint infection (PPJI); however their utility in patients with inflammatory arthritis is unknown. The purpose of this study is to determine the utility of these tests in patients with inflammatory arthritis.
Methods
934 Consecutive revision hip and knee arthroplasties were prospectively evaluated for PPJI. 202 Cases were excluded due to acute post-operative or hematogenous infection. 690 Patients had non-inflammatory and 42 had inflammatory arthritis. Receiver operating characteristic (ROC) curves were used to establish optimal ESR, CRP, WBC, and % neutrophil values for diagnosis of PPJI, and the area under the curve (AUC) was calculated to determine the overall accuracy.
Results
The optimal thresholds for predicting PPJI were ESR 30mm/hr, CRP 17mg/L, WBC 2667, and differential 75% neutrophils in inflammatory arthritis, and ESR 32mm/hr, CRP 15mg/L, WBC 4000, and 78% neutrophils in non-inflammatory arthritis. The efficacy of these tests was similar in both populations (AUC for inflammatory ESR=86.2%, CRP=86.2%, WBC=93.8, 93.6% neutrophils; AUC for non-inflammatory ESR=85.2%, CRP=90.2%, WBC=94.5, 95% neutrophils); there was no significant difference between groups (ESR p = 0.861, CRP p= 0.549, WBC p=0.8315, % neutrophils p=0.7021). The rate of PPJI was significantly higher in patients with inflammatory (33.3%) than non-inflammatory (18.8%) arthritis (p-value=0.013).
Conclusions
These results suggest that the ESR and CRP are useful in diagnosing PPJI in patients with inflammatory as well as non-inflammatory arthritis with similar optimal cut-off values.
