Biomarkers for rheumatoid and psoriatic arthritis

•Many different types of biomarkers have been discovered in RA and PsA patients.•Even though RA and PsA have similar clinical characteristics, most biomarkers are different.•The major difference between RA and PsA is the presence of autoantibodies in RA and absence in PsA.•In the future, multiple biomarkers should be measured longitudinally within one cohort.

Rheumatic diseases, such as rheumatoid and psoriatic arthritis are systemic inflammatory conditions characterized by a chronic form of arthritis, often leading to irreversible joint damage. Early treatment for patients with rheumatic diseases is required to reduce or prevent joint injury. However, early diagnosis can be difficult and currently it is not possible to predict which individual patient will develop progressive erosive disease or who may benefit from a specific treatment according to their clinical features at presentation. Biomarkers are therefore required to enable earlier diagnosis and predict prognosis in both rheumatoid arthritis and psoriatic arthritis. In this review we will examine the evidence and current status of established and experimental biomarkers in rheumatoid and psoriatic arthritis for three important purposes; disease diagnosis, prognosis and prediction of response to therapy.