[Optimal Treatment for Rheumatoid Arthritis with Companion Diagnostics]

The medical strategy for rheumatoid arthritis (RA) has markedly advanced in recent years. The introduction of biologics in addition to methotrexate, an anchor drug, has made it possible to not only suppress pain and inflammation (clinical remission), but also inhibit joint destruction (structural remission), leading to cure from the disease. Since the condition and pathology are heterogeneous among individual patients, optimal treatment for each patient based on the use of companion diagnostics is desired (precision medicine). ACPA is important to diagnose RA, but also to assess the prognosis. ACPA is also a part of companion diagnostics for preclinical RA because it has been found to be positive before the onset. Treatment should be performed under consideration of the disease state such as activity, prognosis regarding joint destruction, and complications. It is also important to clarify the patient characteristics, such as responsiveness to the drugs and risk of adverse effects. Biomarkers, such as proteomics and pharmacogenomics, have been reported as companion diagnostics for optimal treatment of RA. RA is a multifactorial disorder with clinically heterogeneous features. Gene-environment interaction is closely involved in the production of ACPA, and then secondary stimuli to joints may lead to symptoms of RA. Joint injury, emotional stress, and infections often trigger the onset of RA. It is possible to cure RA, achieving complete remission, by early aggressive treatment and returning to the pre-clinical state with environmental improvement. [Review]