Periprosthetic joint infection is a catastrophic complication after joint replacement, and with the rise in the number of joint replacement patients in China, the number of patients with periprosthetic joint infection has also increased, thus making a more accurate diagnosis of periprosthetic joint infection a hot topic of research for orthopedic surgeons. The purpose of this study was to assess the diagnostic value of ESR to C-reactive protein ratio in the diagnosis of patients with periprosthetic joint infections.

We retrospectively analyzed 81 patients hospitalized from January 2015 to December 2020, with periprosthetic joint infections diagnosed according to the Bone and Muscle Infection Society Infection Diagnosis 2014 Revised criteria. In this study we compared the diagnostic efficacy between the combined application of the ESR to C-reactive protein ratio and the classical diagnostic index ESR to C-reactive protein.

In this study 46 cases were in the aseptic loosening patient group and 35 cases in the periprosthetic joint infection group; 32 men and 49 women; the mean age of patients in the infected and non-infected groups was 64.7 ± 12.2 and 61.8 ± 12.9 years old, respectively. The ESR, C-reactive protein, ESR/C-reactive protein ratio and white blood cell count were higher in the infected group than in the non-infected group. The ESR to C-reactive protein ratio had a sensitivity of 89.1% and specificity of 82.7%, with an AUC of 0.882 significantly higher than that of ESR (AUC, 0.831) and comparable to that of C-reactive protein (AUC, 0.889). The ESR to C-reactive protein ratio had a higher specificity and positive predictive value compared to other indices.

The ESR to C-reactive protein ratio is a new index for the diagnosis of periprosthetic joint infection and helps to accurately differentiate periprosthetic joint infection from aseptic loosening.