Chisari E, Yacovelli S, Goswami K, Shohat N, Woloszyn P, Parvizi J.

The Journal of Arthroplasty. 2021;36(8):2942-2945.e1.
doi: 10.1016/j.arth.2021.03.006

Summary by Saad Tarabichi MD

Periprosthetic joint infection (PJI) is a catastrophic complication and a significant cause of implant failure after total joint arthroplasty (TJA).¹ Recent studies demonstrate that PJI incurs substantial costs to patients while also significantly burdening healthcare systems.² Unless there is clear evidence of infection, such as the presence of a sinus tract, the diagnosis of PJI typically involves the use of synovial and/or blood biomarkers.³ Synovial leukocyte esterase (LE) is a particularly useful biomarker for PJI diagnosis. Moreover, the LE strip test is rapid, inexpensive, and widely available. The LE strip test grades the presence of LE as negative, trace, 1+, or 2+. When compared to the Musculoskeletal Infection Society (MSIS) criteria for PJI, the sensitivity and specificity of LE is reported to be between 92.9%-100% and 77.0%-88.8%, respectively.⁴ However, no study has evaluated the accuracy of LE with respect to the more recently developed guidelines by the International Consensus Meeting (ICM) on Musculoskeletal Infections to help clinicians establish a working diagnosis of PJI.⁵

This was a retrospectively reviewed study of patients undergoing revision total hip arthroplasty (THA) or total knee arthroplasty (TKA) at a single institute spanning a 10-year timeframe. The inclusion criteria required all patients to have a comprehensive workup for PJI as per the ICM criteria, as well as a diagnosis of osteoarthritis prior to the primary surgery. Two hundred fifty-nine patients undergoing revision TKA or THA were included. To investigate the diagnostic performance of LE, synovial fluid was collected via aspiration intraoperatively.

Of the 259 patients, 79 underwent revision surgery for PJI (30.8%) and 181 for aseptic failure (69.2%). The average age and BMI of the cohort was 65.3 +/- 10.7 years and 32.3 +/- 5.96 kg/m², respectively. The ability of LE to accurately diagnose PJI varied with the cutoff for positivity. At a cutoff of “1+ and greater,” the LE test had a sensitivity of 0.744, specificity of 0.906, positive predictive value of 0.773, and a negative predictive value of 0.891. At a cutoff of 2+ for LE positivity, specificity improved to 1.00 and sensitivity dropped to 0.513.

The LE strip test is a rapid and inexpensive test that can be administrated at point of care. Using the ICM criteria as a benchmark for PJI diagnosis, LE demonstrated valuable performance and reliable results. For optimal outcomes, an LE cutoff of “1+ and greater” is recommended by the authors of the study. An LE cutoff of 2+ demonstrated near perfect specificity for the diagnosis of PJI, at the cost of decreased sensitivity. Additionally, this study reinforces the incorporation of the LE strip test in the ICM criteria. A limitation of this study is the subjective interpretation of the colorimetric response of the LE strip test.

References

1. Ashley BS, Parvizi J. Current Insights in the Evaluation and Treatment of Infected Total Knee Arthroplasty. The Journal of Knee Surgery. Published online October 2, 2021. doi:10.1055/s-0041-1737030
2. Kurtz SM, Lau E, Watson H, Schmier JK, Parvizi J. Economic burden of periprosthetic joint infection in the United States. The Journal of arthroplasty. 2012;27(8 Suppl):61-5.e1. doi:10.1016/j.arth.2012.02.022
3. Chisari E, Parvizi J. Accuracy of blood-tests and synovial fluid-tests in the diagnosis of periprosthetic joint infections. Expert Review of Anti-infective Therapy. 2020;18(11):1135-1142. doi:10.1080/14787210.2020.1792771
4. Parvizi J, Tan TL, Goswami K, et al. The 2018 Definition of Periprosthetic Hip and Knee Infection: An Evidence-Based and Validated Criteria. The Journal of Arthroplasty. 2018;33(5):1309-1314.e2. doi:10.1016/j.arth.2018.02.078
5. Schwarz EM, Parvizi J, Gehrke T, et al. 2018 International Consensus Meeting on Musculoskeletal Infection: Research Priorities from the General Assembly Questions. Journal of Orthopaedic Research. 2019;37(5):997-1006. doi:10.1002/jor.24293