Leukocyte Esterase Versus ICM 2018 Criteria in the Diagnosis of Periprosthetic Joint Infection

Background: A leukocyte esterase (LE) test is inexpensive and provides real-time information about patients suspected of periprosthetic joint infections (PJIs). The 2018 International Consensus Meeting (ICM) recommends it as a diagnostic tool with a 2+ cutoff. There is still a lack of data revealing LE utility versus the ICM 2018 criteria for PJI. Methods: This is a retrospective study of patients who underwent revision total hip and total knee arthroplasty at a single institution between March 2009 and December 2019. All patients underwent joint aspiration before the arthrotomy, and the LE strip test was performed on aspirated joint fluid. PJI was defined using the 2018 ICM criteria. Results: As per the 2018 ICM criteria, 78 patients were diagnosed with chronic PJI and 181 were not infected. An LE test with a cutoff of ≥1+ had a sensitivity of 0.744, a specificity of 0.906, a positive predictive value of 0.773, an accuracy of 0.825 (95% confidence interval 0.772-0.878), and a negative predictive value of 0.891. The positive likelihood ratio (LR+) was 7.917. Using an LE cutoff of 2 + had a sensitivity of 0.513, a specificity of 1.000, and an accuracy of 0.756 (95% confidence interval—0.812). Conclusion: LE is a rapid and inexpensive test which can be performed at the bedside. Its performance is valuable as per ICM criteria. Based on the findings of this study and the given cohort, we suggest using the cutoff of LE1+ (result = negative or trace) as a point of care test to exclude infection, whereas LE at 2 + threshold has near absolute specificity for the diagnosis.