Common test appears accurate in helping diagnose joint infection


Researchers continue to seek better ways to diagnose and subsequently treat periprosthetic joint infection (PJI) in patients following total joint arthroplasty. A prospective study conducted by researchers at Jefferson Medical College’s Rothman Institute shows that leukocyte esterase reagent (LE) strips, common in diagnosing urinary tract infections, can also have a role in rapid diagnosis of PJI.

The study built on previous work focused on developing a better, faster way to diagnose PJI.

“Our continued research will help us get to the root cause of PJI and therefore enable us to diagnose this terrible condition expeditiously, inexpensively, and with minimal risk to patients,” said Javad Parvizi, MD, FRCS, director of research at the Rothman Institute and professor of orthopedics at Jefferson Medical College in Philadelphia.

The findings on the use of LE strips were presented at the American Academy of Orthopedic Surgeons annual meeting in San Francisco on February 7.

The researchers noted that antibiotic-resistant organisms have increased the prevalence of post-surgical periprosthetic infections. Deep periprosthetic joint infection is the most common indication for revision of total knee arthroplasty and the third most frequent indication for revision of total hip arthroplasty.

The team hypothesized that enzymes secreted by neutrophils may be markers for infection. They tested the sensitivity and specificity of a method for detecting one of those enzymes, leukocyte esterase. Esterase is released by white blood cells and is associated with other types of bacterial infections, including urinary tract infections.

They performed intraoperative aspirations on 117 patients between 2007 and 2009 and tested for the presence of leukocyte esterase using a simple colorimetric strip test. Color change, denoting the presence and level of enzyme, was recorded.

Of those tested, 23 were infected and 94 were determined to be uninfected. When using the highest level of infection as the threshold for a positive test, the test was 86.4 percent sensitive for infection and 95.8 percent specific for esterase, the researchers reported. When using the smallest level of detected infection as the threshold, the test was found to be 59.9 percent sensitive and 98.8 percent specific.

“While this is our first test of LE strips for use in diagnosing PJI, our findings show the test to be accurate for detecting infection in the synovial fluid. This is encouraging as we continue in our research to better understand, detect and treat PJI in our patients,” said Parvizi.

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