The present invention provides a method of determining the rheumatoid arthritis status of a subject, or the progression of rheumatoid arthritis, or the appropriate treatment for a subject with rheumatoid arthritis, comprising the steps of (a) determining the level of tenascin-C in a sample from said subject； and (b) comparing the level of tenascin-C determined in step (a) with one or more reference values. Preferably the rheumatoid arthritis referred to is erosive rheumatoid arthritis. The be accompanied when published by FIG. 5.
