Interpretation of Leukocyte Esterase for the Detection of Periprosthetic Joint Infection Based on Serologic Markers

Leukocyte esterase (LE) is a rapid, point-of-care test for periprosthetic joint infection. The purpose of this study was to provide a tool for interpreting LE based on an initial serologic screening.

We reviewed the records of 319 patients who had erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) screening before hip or knee aspiration; 102 had elevated ESR and CRP levels, 64 had an elevated ESR or CRP level, and 153 had normal serology. The likelihood of infection was calculated based on the results of LE testing.

When LE results were concordant with ESR and CRP levels, LE served to effectively diagnose or rule out a diagnosis of periprosthetic joint infection with >95% certainty. When LE was discordant from serology, only the stricter LE thresholds (2+ or negative) were adequately diagnostic to potentially suggest a change in clinical decision-making.

With discordant results, the lesser thresholds (1+ or trace) should serve to incite further diagnostic inquiry.