THE SIGNIFICANCE OF MICROBIAL ANTIGENS, A NTIBODIES AND ANTIGEN-SPECIFIC LYMPHOCYTES IN THE DIAGNOSIS OF INFECTION-RELATED ARTHRITIS

In the differential diagnosis of infection-related arthritis (infectio us arthritis, viral arthritis, reactive arthritis or Reiter's syndrome , Lyme disease) various laboratory methods are applied for the detecti on of the inciting antigen, specific antibodies or microbespecific T-l ymphocytes. In infectious (septic) bacterial or fungal arthritis, the definitive diagnosis can be made only by recovering the organism from the synovial fluid or membrane. Also, in reactive arthritis following extraarticular infection with Yersinia, Salmonella, Shigella, Campylob acter, or Chlamydia, one of the major shifts in perception of disease pathogenesis has been the detection of bacterial determinants by immun ological methods and polymerase chain reaction (PCR) actually within t he joint. In sexually acquired reactive arthritis, the etiologic diagn osis should be based on the direct detection of the pathogen (mainly C . trachomatis) from the urogenital smear specimen. For clinical routin e, serological tests for bacteria specific antibodies (IgM and IgA cla ss) are often necessary to show recent or persistent infection with th e triggering pathogen. However, a cautionary note regarding the diagno stic significance of antibacterial antibody profiles has been sounded in several studies because of the high prevalence of bacteria-specific antibodies in the healthy population. The same problem may arise in t he interpretation of virus-specific antibodies in the differential dia gnosis of acute polyarthritis. Antigen-specific proliferation of synov ial fluid lymphocytes can confirm the clinical diagnosis in patients w ith reactive arthritis and Lyme disease, although unspecific prolifera tion to several bacteria can also be observed in reactive arthritis as well as in many other arthritis.