The CRP/Albumin Ratio as a Prognostic Indicator to Guide the Timing of Reimplantation in Prosthetic Joint Infection: A Multicentre Analysis

Introduction The optimal timing for reimplantation following two-stage exchange for chronic periprosthetic joint infection (PJI) remains elusive and subjective. In response to inflammation from infection, the liver produces more C-reactive protein (CRP) and increased vascular permeability leads to a decrease in serum albumin. With the resolution of infection, the opposite trend is observed. We theorize that a ratio of these values could guide timing of reimplantation. The purpose of this study is to determine if the recurrence of PJI correlates with the CRP-albumin ratio. Methods Patients who underwent a two-stage exchange for chronic PJI at two institutions were retrospectively reviewed. Patients that had albumin and CRP level at least 8 weeks post-resection and before reimplantation, with minimum 2-year follow-up were included. Seventy-two patients met final inclusion criteria. The primary outcome was recurrence of PJI. The CRP/albumin ratio was analyzed with receiver operating characteristic curves (ROC) for response failure. Results Eleven of 72 (15.3%) of patients had recurrence of infection (4/27 hips and 7/45 knees). The CRP/albumin ratio was higher in the recurrence group than in the success group (1.0 ± 0.7 vs 0.4 ± 0.5, p<.001). The mean CRP level was higher in the recurrence group than in the success group (3.4 ± 2.3 mg/dL vs 1.6 ± 1.9 mg/dL, p=.006). Similarly, the mean albumin level was lower in the failure group than in the success group (3.4 ± 0.8 g/dL vs 4.0 ± 0.4 g/dL, p<.001). ROC analysis of the CRP/albumin ratio found an area under the curve of .79, which represents a “fair” marker of recurrent infection risk. Utilizing Youden's J statistic to maximize sensitivity and specificity, the optimal cut-off for the CRP/Albumin ratio was determined to be 0.46. Patients with a CRP/albumin ratio ≥0.46 had a higher risk of recurrence of PJI (OR 12.7, p=0.0023) Conclusion A higher CRP/albumin ratio prior to reimplantation correlated with increased risk of recurrence of PJI following two-stage exchange arthroplasty. This diagnostic marker may help surgeons determine appropriate timing for reimplantation.