Tracking Disease Activity in Inflammatory Arthritis
Learn how doctors determine if your disease is progressing or improving
Your rheumatologist is treating you for inflammatory arthritis. But how do you know the treatment’s working? That’s easy. You have less pain, and your doctor can see your joints aren’t as swollen. That’s been the traditional approach – using a combination of clinical judgment and patient self-reports to track disease activity. But with more complex regimens and an emphasis on treating to pre-determined targets, doctors increasingly rely on sophisticated measurement tools instead. Some studies suggest these tools may do a better job of getting patients to remission. But there’s a problem. Many were developed for clinical studies and may be too expensive and time-consuming for regular use, so researchers are trying to make the tools friendlier. Interestingly, the modifications look a lot like the old way of doing things since many give primary importance to patient input.
The American College of Rheumatology recommends six tools for measuring disease activity in rheumatoid arthritis (RA). They fall into three main categories:
- Patient questionnaires. Some, like the visual analog scale (VAS) ask you to rate your pain. Others ask how much trouble you have performing daily activities, like dressing or bathing.
- Joint counts. The most common of these tests is DAS28, which generates a disease activity score based the degree of swelling and inflammation in 28 different joints.
- Lab tests. Erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) measure body-wide inflammation.
Most ACR measurement tools include something from each of the three categories. The data are plugged into a formula that produces a number that shows how well your disease is controlled. If your score goes up, it means your disease activity is worse and it may be time to change your treatment.
Susan Goodman, MD, a rheumatologist at Hospital for Special Surgery in New York, says three of the tools – DAS28, RAPID3 and simplified disease activity index (SDAI) – are used most often. RAPID3, a patient questionnaire, takes just seconds to score and may be as accurate as more complicated measures.
Psoriatic Arthritis (PsA)
PsA is much more complex than RA. It not only attacks the joints, but also can affect your skin, spine, nails, eyes and ligaments. Disease activity measures that encompass such a broad range of symptoms have been challenging to develop, and the most common ones have limitations.
For example, the Disease Activity Index for Psoriatic Arthritis (DAPSA) is relatively easy to use but doesn’t include skin symptoms – one of the hallmarks of psoriatic arthritis. The Psoriatic Arthritis Disease Activity Score (PASDAS) is complicated and requires that patients fill out a lengthy questionnaire. Allan Gibofsky, MD, a professor at Weill Cornell Medicine in New York City, says measures like these, often developed for clinical trials, “are not as meaningful in clinical practice.”
The solution may be a new, short patient questionnaire called Psoriatic Arthritis Impact of Disease (PsAID). It’s a simple way of looking at the effect of arthritis on a person’s life. Patients rate 12 physical and psychological factors, including skin problems, weight, pain and fatigue on a 10-point scale. A higher score reliably indicates worse disease activity.
Ankylosing Spondylitis (AS)
Like PsA, symptoms in AS vary widely and can include eye and bowel inflammation, heart disease and fatigue. Many rheumatologists think the best measure of disease activity in AS is the ankylosing spondylitis disease activity score (ASDAS). It combines patient self-reports on back pain, stiffness and swollen joints with an inflammation marker such as CRP or ESR. Most patients can answer the four questions in less than a minute and scoring is simple.
Imaging tests like MRI and X-rays shouldn’t be used to monitor AS activity, but some researchers recommend that patients with AS have routine electrocardiograms to check for early heart disease.
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