Measuring Disease Activity in Rheumatoid Arthritis

How do doctors measure disease activity in patients with RA and what do those scores mean?


Most rheumatologists have long relied primarily on their own clinical judgment and intuition when deciding whether a patient with rheumatoid arthritis (RA) requires a change in treatment in order to keep the disease under control. However, there is now solid evidence to suggest that RA patients do best when doctors use a so-called “treat to target” approach—that is, adjust a patient’s therapeutic regimen as necessary to achieve a specific goal.

But the treat-to-target philosophy requires information about an RA patient’s “disease activity”—that is whether his or her condition is improving or getting worse. How can you hit your target unless your doctor knows when to increase a dose or add a drug to your regimen? Yet not all rheumatologists in the United States use available tools for monitoring disease activity in RA.

One reason may be that there is no single “gold standard” test for this purpose that’s comparable to, say, a cholesterol test for a heart patient or a blood sugar assay for a diabetes patient. However, last May, the American College of Rheumatology (ACR) recommended six tools for the systematic measurement of disease activity in RA. Using these tools consistently can help identify small changes that a patient may not notice and that may escape a physician’s observation, says rheumatologist Salahuddin Kazi, MD, of the Dallas VA Medical Center, a coauthor of the ACR guidelines. Responding to these changes as soon as possible with a change in drug treatment can help limit the risk for long-term joint damage, says Dr. Kazi.

The sooner a patient gets the right treatment, the less likely he or she will suffer long-term joint damage, Dr. Kazi points out. “It’s like a front-loaded mutual fund,” he says. “You have to make that early investment to see your returns.” Your doctor can’t literally feel your pain, but could he or she help to ease it by using formal tools to track your disease activity?

Many Tools Available

While there may be no acknowledged “best” test for measuring disease activity in RA, dozens of such methods have been devised over the years. Broadly speaking, these tests fall into three categories:

  • Patient questionnaires. A simple version of such a test is the Visual Analog Scale (VAS), which features a horizontal line with the words NO PAIN on the left and WORST PAIN on the right; the patient makes a mark on the line to indicate the point on the spectrum that reflects how he or she is feeling. Other patient-focused tests are more detailed. For example, some ask questions about how much difficulty the patient has performing daily activities, such as bathing, dressing and climbing in and out of cars.
  • Joint counts, in which a doctor examines a specific set of a patient’s joints and tallies the number that are swollen and/or tender. The most common of these tests is the DAS28, which generates a “disease activity score” (hence the acronym “DAS”) based on an examination of 28 joints in the shoulders, arms, hands and knees.
  • Lab tests that measure markers of inflammation. The most widely used measurements are erythrocyte sedimentation rate (ESR), which tracks how fast red blood cells fall in a test tube, and C-reactive protein (CRP), which is manufactured in the liver and rises when inflammation is present.

Most of the ACR-approved measurement tools combine one or more of these elements. For example, the DAS28 combines a joint count, lab test (either the ESR or CRP), and a VAS. This data is plugged into a formula, which produces a number between 0 and 10 that reflects how well the patient’s RA is controlled; if the number continually rises over time, a change in treatment is probably in order. In a British study, researchers followed 111 RA patients. Half of the study subjects were cared for by physicians who relied on their own subjective observations to determine whether a patient’s arthritis was improving or worsening. The other half saw physicians who used DAS28. Two years later, 65 percent of the patients tracked with DAS28 were in remission, compared to just 16 percent of patients in the usual-care group.

However, the DAS28—like most disease-activity measuring tools—was designed for use in clinical studies, and some doctors find it too time-consuming and complicated to use in a busy clinic. Rheumatologist Nathan Wei, MD, of Frederick, Md., occasionally uses the DAS28 in his practice. “Some days I’m a DAS user, some days I’m not,” says Dr. Wei.

“I spend more time asking patients, ‘How are you doing?’” says Dr. Wei. He’ll then consider what the patient says about his or her condition, the results of lab tests, and an occasional imaging exam (usually an MRI) to make treatment decisions.

However, some rheumatologists appear to be less interested in what their patients tell them. “There is reluctance to accept the patient’s version of the story,” says Dr. Kazi, noting that some physicians end up thinking that many of the people they treat are chronic complainers who overestimate their pain. Not surprisingly, surveys show that rheumatologists place a much higher value on joint counts than on patient feedback when formulating treatment plans.

Yet studies also show that patient questionnaires—which are easy to use and require no time or effort on behalf of the physician—can be as effective as the DAS28 and other clinical assessment tools for monitoring disease activity in RA. One ACR-endorsed tool, the Routine Assessment of Patient Index Data 3 (RAPID3), asks patients how limited they are in performing specific daily activities, whether they are having sleep or emotional difficulties, and to rate their pain and overall health on a scale of 0 to 10.

“The RAPID3 takes about a minute to complete, seconds for a nurse to grade, and then you have a numerical value of how a patient is doing,” says Patricia Daul, RN, executive director of clinical services at Buffalo Rheumatology.

RA patients at Daul’s clinic are monitored with regular VAS and RAPID3 testing, which she says has improved care, in part by helping patients stay motivated to keep taking their medications, which may not produce obvious results right away.

“Sometimes we’re like cheerleaders, trying to keep patients on therapy,” says Daul. When a patient complains that her medication isn’t working, Daul can point to how his or her test scores have improved over time. That’s often all the motivation a patient needs to stay the course and keep taking his or her prescribed medications.

If your doctor doesn’t currently use a formal tool for tracking RA disease activity, that will probably change before long. Medicare will soon require physicians to show evidence that they used a scale or test of some kind to measure disease activity in their RA patients, and observers predict that other third-party payers will follow suit.

Dr. Kazi says that doctors still need to use their training and clinical judgment when treating RA patients. Yet it’s clear that adding any of the ACR-endorsed tests can help patients better manage your RA.

“There’s no advantage of one tool over another. They all have reasonable evidence of validity,” says University of Arkansas rheumatologist Nasim Khan, MD, who studies methods for measuring disease activity in RA patients.

Dr. Khan believes a growing number of rheumatologists are discovering the power of routine testing. “More and more practices are adopting some objective fashion of documenting RA activity and making decisions based on that,” he says. “That’s a good thing.”

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