Leukocyte esterase (LE) strip test is an accurate marker for diagnosing periprosthetic joint infection (PJI). This study aims to determine if LE is a good predictor of persistent infection and/or subsequent failure in patients undergoing reimplantation.
This single-institution study prospectively recruited and retrospectively analyzed 109 patients who underwent two-stage exchange treatment of PJI, from 2009-2016, and had an LE test performed at time of reimplantation. LE results of “2+” were considered positive. Ninety-five patients had 90-day minimum follow-up to assess treatment failure, defined by Delphi criteria. Eighteen patients were excluded due to blood contamination of LE test, resulting in a final cohort of 77 patients (mean follow-up 1.76 years).
Of the final cohort, 19 patients (24.7%) experienced subsequent failure. At reimplantation, LE test was positive in 22.2% of culture-positive and 4.4% of culture-negative cases. The LE test was negative in all patients who had not failed at latest follow-up, yielding sensitivity, specificity, positive predictive value, negative predictive value, and AUC of 26.3%, 100%, 100%, 87.5%, and 0.632, respectively; in comparison, MSIS criteria respectively yielded 25.0%, 87.3%, 27.6%, 85.8%, and 0.562 (P = .01 for specificity). Kaplan-Meier curves revealed higher failure rate in patients who had a positive LE test at time of reimplantation (P < .001).
There is a dire need for an accurate diagnostic test to determine optimal timing of reimplantation in patients undergoing surgical treatment for PJI. The current study suggests that a positive LE test may be indicative of persistence of infection and results in a higher rate of subsequent failure.