To compare the conclusions of studies addressing the outcome of early-arthritis cohorts.
The methodologies of previous reports on early-arthritis cohorts were examined, and their results and conclusions were compared.
Thirty-four reports on 23 cohorts of early arthritis were found. The methodology was poor in most studies, with numerous inclusion and exclusion biases, frequently short follow-up periods, and a lack of precision about the rationale for diagnosis. However, similar conclusions were reached on several points: a large number of cases of early arthritis remained undifferentiated and/or resolved spontaneously, about 80% of cases initially classified as undifferentiated or rheumatoid arthritis retained this diagnosis during follow-up, and the incidence of psoriatic arthritis in most studies was similar (2% to 4%). Conversely, there were striking discrepancies among studies concerning the frequency of crystal arthropathies (0% to 18%), spondyloarthropathy (1% to 33%) and rheumatoid arthritis (15% to 47%).
Recognition of cultural bias in the diagnosis of early arthritis could be a prerequisite for the optimization of new sets of criteria for the diagnosis of early rheumatoid arthritis and spondyloarthropathy.
There appears to be a lack of agreement among researchers about the nosology and/or taxonomy of many cases of mild arthritis, despite the existence of classification criteria.