Predicting response to treatment in patients with rheumatoid arthritis

Recently, great progress has been made in dissecting the criteria-based syndrome of rheumatoid arthritis (RA) into subgroups shown to have different pathogenic mechanisms. In parallel, several effective immunologically designed treatments have become available for standard care and have changed the prognosis for RA patients profoundly. However, we know that the disease course varies widely between patients and we also know that each of the new biological therapies is usually very effective in about one-third of patients, partially in one-third, while one-third does not respond at all. The non-responders may still respond well to another drug, maybe because it modifies another pathogenic pathway that presumably might be more prominent in the disease pathogenesis in that patient. The aim of this review is to give a broad 'state-of-the-art' picture of the quickly expanding literature on potential predictors of treatment response in RA, as well as explain which measures are currently recommended for defining response.