What is the role of arthrocentesis, synovial fluid analysis, and synovial biopsy in the workup of reactive arthritis (ReA)?

Updated: Dec 24, 2020
  • Author: Carlos J Lozada, MD; Chief Editor: Herbert S Diamond, MD  more...
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Arthrocentesis and fluid analysis are often needed to rule out an infectious process, especially in monoarticular arthritis with constitutional symptoms. Synovial fluid analysis reveals a high WBC count (10,000-40,000/µL), most often with polymorphonuclear leukocytes (PMNs) predominating. CH50, C1INH, C4, C5, and C3 levels are elevated. Gram stain and culture results are negative and are necessary to exclude septic arthritis. Microbial components and antigens have been identified in joint fluid using sophisticated laboratory techniques.

PCR assay has been used to detect Chlamydia and Yersinia antigenic DNA in synovial fluid, but these organisms are highly prevalent in the control population, and results have varied considerably from one institution to another. [41] Synovial fluid PCR has led to the detection of bacterial antigenic material in as many as 50% of patients previously diagnosed with undifferentiated spondyloarthropathy. [90]

Synovial biopsy typically yields nonspecific inflammatory changes; infectious antigens have been found in the synovium. Immunohistochemistry (IHC), PCR assay, and molecular hybridization may become more useful.

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