The Change of Serum Interleukin-6 Fails to Identify Subsequent Periprosthetic Joint Infection in Patients Who Have Two-Stage Revision for Periprosthetic Joint Infection.

BACKGROUND

The diagnosis of persistent infection prior to second-stage reimplantation in 2-stage exchanges for periprosthetic joint infection (PJI) can be challenging as there is no optimal diagnostic tool. This study investigates the usefulness of pre-reimplantation serum C-reactive protein (CRP) and interleukin-6 (IL-6) and its change between both stages to identify patients who have subsequent PJI.

METHODS

There were 125 patients who underwent planned 2-stage exchange for chronic knee or hip PJI from a single center retrospectively identified. Patients were included if preoperative CRP and IL-6 were available for both stages. Subsequent PJI was defined as 2 positive microbiological cultures at reimplantation or subsequent surgery or death due to PJI during follow-up.

RESULTS

Prior to reimplantation, the median serum CRP (total knee arthroplasties [TKAs]: 1.0 versus 0.5 mg/dL, P = .028; total hip arthroplasties [THAs]: 1.3 versus 0.5 mg/dL, P = .015) and median IL-6 (TKA: 8.0 versus 6.0 pg/mL, P = .052; THA: 7.0 versus 6.0 pg/mL, P = .239) were higher in patients who had subsequent PJI. The IL-6 and CRP values showed moderate sensitivity (TKA/CRP: 66.7%; THA/CRP: 58.8%; TKA/IL-6: 46.7%; THA/IL-6: 35.3%) and good specificity (TKA/CRP: 66.7%; THA/CRP: 81.0%; TKA/IL-6: 86.3%; THA/IL-6: 83.3%). The change in CRP and IL-6 between the stages did not differ between the groups, respectively.

CONCLUSIONS

Serum CRP and IL-6 show low to moderate sensitivity and good specificity in the diagnosis of subsequent PJI prior to reimplantation, which questions their usefulness as a rule-out test. Furthermore, the change in between stages does not appear to identify subsequent PJI.