What have we learnt from early rheumatoid arthritis cohorts?

Longitudinal and observational studies have provided valuable information on the course, clinical outcomes, and prognostic markers in rheumatoid arthritis (RA). They reflect a complete spectrum of disease in 'true-to-life' settings, and can identify aspects of RA such as long-term outcomes and predictive markers which are not easily obtained from clinical trials. Profiles of drug therapies gained over time from these studies complement those of short-term randomized studies. Comparisons of results from early-RA cohorts show both similarities and considerable differences.