Classification of the spondyloarthropathies

The spondyloarthropathies are a group of conditions which share similar clinical features. Classification criteria permit separation of the conditions, allow better targeting of therapies, better measurement of outcomes, and better prognostic information. Early diagnosis remains problematic, but validated criteria for established disease are now emerging.

Histopathology and histochemistry are providing a better understanding of the underlying process of inflammatory arthritis in spondyloarthropathy and other inflammatory arthritides. Early disease, however, continues to challenge current criteria. Sophisticated imaging with magnetic resonance imaging is being increasingly used and is proving useful for early diagnosis as well as helping to understand the pathophysiology of disease. Juvenile idiopathic arthritis continues to provide problems and criteria have recently been modified to allow a greater clinical utility and inclusion of more patients. Poststreptococcal reactive arthritis appears to be a heterogeneous clinical entity, with a group looking more like rheumatic fever and a group with spondyloarthropathy traits. It may be that the association is not streptococcal, but is a throat infection. Currently available criteria for psoriatic arthritis have been evaluated in a large cohort. Four of the criteria performed well with high specificity and sensitivity whereas the other two had moderate specificity and low sensitivity. It was shown that rheumatoid factor positivity does not exclude a diagnosis of psoriatic arthritis--the single most important clinical feature of this condition being the presence of psoriasis.

The spondyloarthropathy classification criteria continue to be an area of development. This is most apparent in juvenile arthritis and psoriatic arthritis. The latter is currently undergoing intense scrutiny to develop classification criteria and outcome measures.