How is Reactive Arthritis diagnosed?
A diagnosis of reactive arthritis involves the pattern of joint involvement and timing of the onset of arthritis following infection.
Diagnosis of reactive arthritis (including the condition formerly called Reiter’s syndrome) is mainly clinical. There are no validated diagnostic criteria, however some guidance for diagnosis is available. [18, 19, 20, 10]
In 1995, the Third International Workshop on Reactive Arthritis established criteria for diagnosing reactive arthritis. The main criteria involve the pattern of joint involvement and the timing of the onset of the condition (such as soon after an infection). Diagnosis of Reiter’s syndrome has essentially been replaced with diagnosis of the broader category in which it resides: Reactive Arthritis.
The diagnostic criteria of the Third International Workshop on Reactive Arthritis are:
- The arthritis should predominantly involve the lower limb, involve one or only a few joints and not equally involve both sides of the body (asymmetric).
- There should be evidence or a history of preceding infection. Although it is ideal to have a culture that is positive for an infectious agent that is recognized to be associated with this condition (such as Salmonella or Chlamydia), if the patient has documented diarrhea or urethritis in the prior 4 weeks, laboratory confirmation is not required.
- If there is no clear clinical infection, then laboratory confirmation (perhaps with serology or a culture) is essential.
- The patient should not have evidence that the joint itself is infected (i.e., septic arthritis). Also, other causes of monoarthritis (such as gout) or oligoarthritis (such as rheumatoid arthritis) should be ruled out.
Interestingly, the above criteria do not require laboratory tests (such as HLA-B27). Features that have been considered part of Reiter’s syndrome such as conjunctivitis, iritis, skin lesions, noninfectious urethritis, and certain types of cardiac and neurological abnormalities are not required for a diagnosis of reactive arthritis.