Diagnostic Value of CRP and Serum WBC Count during Septic Two-Stage Revision of Total Hip Arthroplasties

Abstract

The diagnostic value of C-reactive protein (CRP) and the serum white blood cell (WBC) count is still barely defined for decision making during septic two-stage revision surgery of hip arthroplasty. We, therefore, compared these values between stages as well as between the groups without and with reinfection in 117 patients. A total of 106 patients were reinfection-free (91%). The median follow-up was 51 months. With a ΔCRP of -10 mg/L and a ΔWBC count of -1000/µL, a significant decrease between stages (p = 0.001) could be observed. When comparing the CRP and WBC count values between groups, however, no significant difference was found at stage one, stage two and even the difference between these two time points (reinfection-free ΔCRP of -11 mg/L and ΔWBC count of -1000/µL vs. reinfection ΔCRP of -5 mg/L (p = 0.131) and ΔWBC count of -1100/µL) (p = 0.424). The diagnostic value was poor for the calculated parameters (area under the curve (AUC) 0.5-0.6). The courses of the mean CRP values of both groups were similar. We conclude that the CRP and WBC count are not helpful to guide the decision making in individual cases.

Keywords: CRP; bone and joint infections; hip arthroplasty; infection parameters; orthopedic infections; periprosthetic joint infection; two-stage revision; white blood cell count.

Figure 1

Boxplots for C-reactive protein (“CRP“) values prior to stage-one and prior to stage-two surgeries, divided in groups without and with reinfection.

Figure 2

Boxplots for white blood cell count (“WBC count“) values prior to stage-one and prior to stage-two surgeries, divided in groups without and with reinfection.

Figure 3

Receiver operating characteristic curves for C-reactive protein prior to stage two (“CRP stage two“) and for ΔCRP (CRP stage two minus CRP stage one).

Figure 4

Receiver operating characteristic curves for white blood cell count prior to stage two (“WBC count stage two“) and for ΔWBC count (WBC count stage two minus WBC count stage one).

Figure 5

Mean C-reactive protein (CRP) value preoperatively and in the further clinical course of patients without reinfection (blue curve) and with reinfection (green curve).

Figure 6

The area under the curve (AUC) of the mean C-reactive protein (CRP) values preoperatively and in the further clinical course of cases without reinfection ((a) green curve) and with reinfection ((b) orange curve).