SLR - March 2015 - Nathaniel Preston

Preliminary Results of a New Test for Rapid Diagnosis of Septic Arthritis with Use of Leukocyte Esterase and Glucose Reagent Strips

Reference: Omar, M, Ettinger M, Reichling M, Petri M, Lichtinghagen R, Guenther D, Suero EM, Jagodzinski M, Krettek C. Preliminary Results of a New Test for Rapid Diagnosis of Septic Arthritis with Use of Leukocyte Esterase and Glucose Reagent Strips. J Bone Joint Surg Am. 2014 Dec 17;96(24):2032-7.

Reviewed By: Nathaniel Preston, DPM
Residency Program: Grant Medical Center

Podiatric Relevance: Although septic arthritis is uncommon in the foot and ankle, it should nevertheless remain part of a thorough differential for acutely swollen and painful joints; especially in cases in which wounds probe to the joint capsule or into the joint itself. Septic arthritis can lead to significant destruction of soft tissue and bone if treatment is not initiated quickly making rapid and reliable diagnosis essential.

Methods: Synovial fluid collected over a one year period from arthrocentesis of atraumatic joint at a single institution was prospectively analyzed and tested using a combination of two readily accessible test strips. The synovial fluid was tested using leukocyte esterase and glucose test strips, and results were compared to traditional laboratory testing; leukocyte count, crystal analysis, gram stain, culture and glucose concentration.

A total of 146 synovial fluid samples were used; 19 classified as septic and the remaining 127 being classified as aseptic. Classification was determined using synovial fluid cell count and glucose concentration. The leukocyte esterase reagent test strips used in this study are commonly used for evaluation of urine samples to allow for rapid diagnosis of UTIs on the basis of an elevated leukocyte esterase level. However, leukocyte esterase alone cannot differentiate reliably between septic arthritis and other metabolic forms of arthritis, which may also result in an elevated concentration of neutrophils. To aid in reliable differentiation, glucose level was used; a reduced glucose concentration suggesting an infectious process in which microbial glucose metabolism is occurring.

Results:  Considering septic arthritis to be present when the leukocyte esterase test strip was positive and glucose test strip was negative yielded a sensitivity of 89.5 percent, specificity of 99.2 percent, positive predictive value of 94.4 percent, negative predictive value of 98.4 percent, positive likelihood ratio of 114, and negative likelihood ratio of 0.11.

Conclusions: The diagnosis of septic arthritis usually requires one or more of the following criteria to be met: 1) isolation of a pathogen from synovial fluid, 2) isolation of a pathogen from a source other than synovial fluid combined with a clinical presentation typical of septic arthritis, 3) turbid synovial fluid, or 4) histological or postmortem findings typical of septic arthritis.

Measurement of synovial fluid leukocyte count and PMN percentage is generally considered the most reliable testing modality with both sensitivity and specificity exceeding 80 percent. With a sensitivity of 89.5 percent and specificity of 99.2 percent, the use of a combination of leukocyte esterase and glucose test strips may be a substantially more time-efficient and cost-effective modality in the rapid and reliable diagnosis of septic arthritis in the acute setting.

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