Diagnosis of reactive arthritis

The diagnosis of Reiter's syndrome or reactive arthritis is made on the basis of data on a previous infection, analysis of the clinical picture, data from laboratory and instrumental examination methods, and the results of etiological diagnostics.

Etiological diagnosis of reactive arthritis

Immunological method:

• detection of chlamydia antigen in epithelial cells obtained from scrapings from the urethra and conjunctiva, synovial fluid (direct immunofluorescence analysis, etc.);
• detection of antibodies to chlamydia antigens in blood serum and synovial fluid (complement fixation reaction, direct and indirect immunofluorescence):
  • acute phase of chlamydia or exacerbation of a chronic process - IgM antibodies during the first 5 days, IgA antibodies - within 10 days, IgG antibodies - after 2-3 weeks;
  • reinfection or reactivation of primary chlamydial infection - increased levels of IgG antibodies, IgA antibodies, single IgM antibodies;
  • chronic chlamydia - constant titers of IgG and IgA antibodies;
  • asymptomatic course of chlamydia, persistence of the pathogen - low titers of IgA antibodies;
  • previous chlamydial infection - low titer of IgG antibodies.
• detection of antibodies to intestinal bacteria in blood serum (direct hemagglutination reaction, complement fixation reaction methods).

Morphological method - identification of morphological structures of the pathogen (staining of preparations, immunofluorescence analysis).

Cultural method - isolation of chlamydia (cell culture, chicken embryos, laboratory animals).

Molecular biological method - detection of pathogen DNA (PCR, etc.) The method is used to detect pathogen DNA in the blood and synovial fluid.

Bacteriological examination of feces.

Bacteriological examination of urine.

Diagnostic criteria for Reiter's syndrome:

• chronological connection between the development of the disease and a previous genitourinary or intestinal infection;
• asymmetric arthritis with predominant damage to the joints of the legs, thalalgia, enthesopathy;
• signs of inflammation in the genitourinary tract and eyes;
• detection of antibodies to chlamydia and/or other arthritogenic microorganisms in the blood and/or their antigens in biological materials;
• damage to the skin and mucous membranes;
• presence of HLA-B27.

Differential diagnosis of reactive arthritis

The most common diseases requiring differential diagnosis with reactive arthritis are infectious arthritis, infectious diseases accompanied by arthritis, orthopedic pathology and various forms of juvenile idiopathic arthritis.

The diagnosis of reactive arthritis is made on the basis of diagnostic criteria adopted at the III International Conference on Reactive Arthritis in Berlin in 1995.

According to these criteria, the diagnosis of “reactive arthritis” is valid only if the patient has typical peripheral arthritis, which occurs as asymmetric oligoarthritis with predominant damage to the joints of the lower extremities.

Berlin diagnostic criteria for reactive arthritis

Indicator	Diagnostic criterion
Peripheral arthritis	Asymmetric Oligoarthritis (affecting up to 4 joints) Predominant damage to the joints of the legs
Infectious manifestations	Diarrhea Urethritis Time of onset: within 4 weeks before arthritis develops
Laboratory confirmation of infection	Not necessary, but desirable in the presence of pronounced clinical manifestations of infection Mandatory in the absence of obvious clinical manifestations of infection
Exclusion criteria	Established cause of development of mono- or oligoarthritis: spondyloarthropathy; septic arthritis; crystalline arthritis; Lyme disease; streptococcal arthritis

Clinical signs of infection (diarrhea or urethritis) suffered 2-4 weeks before the development of arthritis are required. Laboratory confirmation in this case is desirable, but not necessary. In the absence of clinical manifestations of infection, its confirmatory laboratory data are taken into account.

Laboratory tests to confirm arthritic infection

Method of examination	Material
Cultural analysis	Cal Synovial fluid Discharge from the urethra
Serological examination - detection of antibodies to arthritogenic microorganisms	Blood Synovial fluid
Polymerase chain reaction - detection of bacterial DNA	Epithelial cells from the urethra Synovial fluid
Immunofluorescence microscopy - detection of bacteria in the synovial membrane	Synovial membrane cells

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