If you have rheumatoid arthritis (RA), you probably have flares — periods when your symptoms suddenly worsen. If your flares are severe or happen often, it could mean it’s time to change your treatment plan. 

What Is a Flare?

You know when you’re having a flare. But defining a flare is harder than you’d think. “Every patient’s and doctor's definition of a flare is different, so whenever you use the word ‘flare,’ [doctors]  don’t even know what it means,” says Daniel Furst, MD, professor of medicine (rheumatology) at University of California at Los Angeles.

Yet the ability to define and also measure flares is key because it helps doctors understand when RA is in remission (low or no disease activity), if medications are effective and when they stop working as well as they should. “If the patient is having many flares or the flares are lasting a long time, that tells us the drugs are not working well enough,” says Dr. Furst.

What Triggers Flares?

No one knows for sure what triggers flares. But some doctors and patients suspect that these factors could play a role:

  • Missed medications. “This a 'real big trigger,' says Vivian Bykerk, MD, associate professor of medicine at Weill Cornell Medical College and director of the Inflammatory Arthritis Center of Excellence at Hospital for Special Surgery in New York
  • Drugs that stop working. “One thing that can cause flares is developing resistance to a drug, particularly a TNF [tumor necrosis factor] inhibitor,” says John Hardin, MD, Arthritis Foundation director of osteoarthritis research and professor of medicine and orthopedic surgery at Albert Einstein College of Medicine in New York.
  • Stress. “My suspicion is that when people’s lives are on super-drive — they’re not sleeping, they’re stressed, maybe something very difficult happened in their life — that could trigger flares,” says Dr. Bykerk. Dr. Hardin adds: “It’s quite likely that stresses that alter endogenous [naturally produced] hormones would be triggers.”
  • Foods. Some patients report feeling better when following certain diets, but “that’s not been a very well-studied area,” says Dr. Hardin.
  • Low vitamin D. Researchers are looking into whether low D levels trigger flares. A small study, published in Therapeutic Advances in Endocrinology and Metabolism in 2012, concluded, “Vitamin D deficiency may be linked to disease severity in RA.”
  • Menstruation. “A lot of young women with RA will notice it’s worse just before their period,” says Dr. Bykerk. A small study, published in Rheumatology in 2010, found some evidence of a link.

How Do Doctors Measure Flares?

Doctors evaluate flares using a combination approach. They ask patients about their symptoms, check for tender or swollen joints and use a variety of lab tests to measure inflammation in the body, including C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) tests.

One specific formula used to measure flares comes from the American College of Rheumatology. It uses the number of swollen joints, the number of tender joints, the CRP or ESR level and the score from a patient’s self-assessment to calculate a number known as the Disease Activity Score 28, or DAS28 (the 28 represents the number of joints examined). The score indicates whether the patient’s disease activity is low, moderate or high.

Tools such as the DAS28 are “the state of the art,” says Dr. Hardin. But he adds, they can be time-consuming to use. “What we would like is something that’s less laborious to put together.”