Synovial fluid analysis with leukocyte esterase reagent strip test

Area of Science:

• Rheumatology
• Clinical Chemistry
• Point-of-Care Testing

Background:

• Distinguishing inflammatory arthritis from mechanical joint effusion is crucial for appropriate patient management.
• Synovial fluid analysis is a standard diagnostic method, but can be time-consuming and resource-intensive.
• Leukocyte esterase reagent strip test (LERST) offers a potentially rapid and cost-effective alternative for assessing joint inflammation.

Purpose of the Study:

• To evaluate the diagnostic accuracy of LERST in differentiating inflammatory arthritis from mechanical joint effusion.
• To compare visual analysis (VA) and automated colorimetric reader (ACR) methods for LERST interpretation.
• To assess the utility of LERST as a point-of-care test in primary care.

Main Methods:

• Synovial fluid samples from 100 patients with non-traumatic joint effusion were analyzed.
• LERST was performed using both visual and automated reader analysis.
• Results were compared against laboratory white blood cell (WBC) count as the reference standard.

Main Results:

• LERST showed moderate sensitivity (47-55%) and high specificity (89-92%) for detecting inflammatory synovial fluid.
• Visual analysis (VA) demonstrated higher positive predictive value (87.5%) compared to automated colorimetric reader (ACR) analysis (89%).
• There was almost perfect agreement between VA and ACR results (kappa 0.70).

Conclusions:

• LERST is a valuable, low-cost tool for detecting inflammation in synovial fluid of native joints, suitable for primary care.
• The test's low sensitivity limits its utility in definitively ruling out inflammatory joint disorders.
• LERST can aid in the initial assessment of joint effusions, guiding further diagnostic steps.