Markers of disease in rheumatoid arthritis.

Substantial progress can be noted in the efforts to demonstrate the usefulness of tissue-related markers of disease in rheumatoid arthritis and other joint diseases. The most informative studies use longitudinal analyses of well-characterized patient groups. Emphasis should be on searching for markers which can be of prognostic significance. New markers need to be assessed in relation to existing ones, such as C-polysaccharide reacting protein and erythrocyte sedimentation rate, which, although not specific, are hard to beat as measures of inflammation. A newly identified matrix component, cartilage intermediate layer protein, has features which make it attractive as a potential cartilage specific marker. Many markers may not in the end prove clinically useful. They will, however, give important insight into pathogenic processes, and may help in evaluating new therapy. Finally, markers originally identified in humans have now proven their value in experimental arthritis.