Pain in people with rheumatoid arthritis follows different trajectories

What is it about?

RA is a painful autoimmune condition. The immune system of a patient with RA responds in an abnormal way to attack the healthy cells in the body and commonly causes swelling and inflammation of the joints in the wrists, hands and feet. The current treatments for RA will manage the inflammation and joint swelling, and can produce impressive improvements. However, pain still lingers on in many people. We aimed to find subgroups of people with RA that have distinctly different experiences of pain throughout 5 years. We examined databases from 3 studies of people with RA; (1) Early RA Network (ERAN), and the British Society for Rheumatology Biologics Register (BSRBR) (2) commencing TNF-α inhibitors or (3) using non biologic drugs (for example, Methotrexate). The measurements were analysed using a technique called Growth Mixture Modelling which divided people into subgroups based on differences and similarities in their pain data for 5 years. The people in the different trajectories were then compared to each other. Each of the 3 studies showed a similar pattern of trajectories. Up to ¼ of people said that their pain improved to almost normal levels. However, most people said they felt persistent pain. When we looked at the blood levels of inflammation markers, we saw that they did not fully account for the differences in pain. Often inflammation was suppressed while pain remained a problem. Some people with early RA started with high levels of pain and improved markedly. However, this trajectory was not seen in the 2 other studies; showing that it was not common in people with long-standing RA.

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Why is it important?

Treatment reduces inflammation in RA, but pain outcomes are still not favourable. Identifying subgroups with poor pain prognosis could enable adjunctive treatment to improve outcome.