Determining False Positive Rates of Leukocyte Esterase Reagent Strip When Used as a Detection Tool for Joint Infection

Use of leukocyte esterase (LE) testing of synovial fluid as an adjunct to the infection workup in total joint arthroplasty patients has been advocated. The purpose of this study was to determine the false positive rate of this test.

Two hundred patients with the diagnosis of degenerative osteoarthritis undergoing a total knee arthroplasty were identified for this study. The knee joint was aspirated under sterile conditions before performing the total knee arthroplasty. The fluid was analyzed with an LE reagent strip.

There were 27 bloody and 17 dry aspirations. One hundred forty-nine patients produced an aspiration that allowed for LE testing. There was 1 positive LE result. The specificity of the LE test was found to be 99.3%.

These data suggest the LE strip as a part of the workup for infection in a native knee should yield few false positive results.