2009 Abstract : 3

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Authors: Jacovides C, Parvizi J, Azzam K, Antoci V, Ghanem E, Rothman Institute, Philadelphia, PA

Title: Diagnosis of Periprosthetic Joint Infection: The Role of a Simple, yet Unrecognized, Enzyme

Purpose: In this prospective study, we tested the sensitivity and specificity of detecting leucocyte esterase produced by neutrophils in diagnosing periprosthetic joint infection.

Methods: From May 2007 to November 2008, intraoperative aspiration was performed on 92 consecutive patients undergoing revision total knee arthroplasty revision. 1-2 cc of synovial fluid was applied to a strip designed to detect the presence of leucocyte esterase, and the rest was sent for leukocyte cell count and culture for correlation. Intraoperative tissue samples were also obtained and sent for culture. Color change was noted immediately and after 2 min. The color change correlates with negative, trace, + or ++ level of leukocyte esterase enzyme. Knees were aspirated after superficial dissection but before arthrotomy to minimize the incidence of bloody samples.

Results: According to clinical, serological and operative criteria, 14 of those knees were deemed to be infected and were treated accordingly. The test was read as positive (+ or ++) in all 14 infected total knee replacements, yielding a sensitivity of 100%, and in 9 out of 78 non-infected total knee replacements (88% specificity). Introperative cultures were negative in two out of the 14 infected knees.

Discuassion and Conclusion: This early report of an ongoing study suggests that testing for leukocyte esterase enzyme in neutrophils is a valuable addition to the diagnostic armamentarium of prosthetic joint infection. The use of the reagent strips adds the advantage of rapid testing with an excellent ability to rule out infection especially in cases where the diagnosis is doubtful.