Measuring Disease Activity in Rheumatoid Arthritis

Different types of tests are used to show whether treatment is working.

By Timothy Gower

In the past, most doctors who treated rheumatoid arthritis (RA) used their instincts and informal questions, like “How are you feeling?” to make decisions about treatment, such as when to change or add a medication in order to get a patient’s symptoms under control. However, a revolution has occurred in the management of RA, now that research strongly indicates patients fare much better when doctors use a “treat-to-target” (T2T) approach.

In T2T, the doctor adjusts a treatment regimen as necessary to achieve a specific goal, which in most cases is remission or low disease activity (that is, no more than a sore joint or two). “To follow a treat-to-target approach, you need to have a target,” says rheumatologist Bryant England, MD, PhD, an assistant professor at the College of Medicine at the University of Nebraska Medical Center.

But how can a doctor tell whether progress is being made toward the goal or whether a new treatment plan is needed? In 2019, Dr. England led a panel of experts, convened by the American College of Rheumatology (ACR), that recommended five effective and practical tools for measuring disease activity in T2T strategies. Another panel chose three tests for evaluating functional status, that is, how much (if at all) RA limits a patient’s ability to perform daily tasks.

If your doctor isn’t using tools to measure your disease activity and functional status, ask why. But first, learn a bit about how they work.

Crunching Numbers

Broadly speaking, tests used to monitor disease activity and functional status in RA fall into three categories:

• Patient Questionnaires. A simple version is the Visual Analog Scale (VAS), which features a horizontal line with the words “No pain” on the left and “Pain as bad as it could be” on the right; you make a mark on the line to indicate the level or pain you are feeling. Other, more detailed health assessment questionnaires (HAQ) ask about how much difficulty you have performing daily activities, such as bathing, dressing and climbing in and out of cars.

• Joint Counts. A doctor examines a specific set of your joints and tallies how many are swollen and/or tender.

Lab Tests. The most widely used tests to measure markers of body-wide inflammation are erythrocyte sedimentation rate (ESR or sed rate) and C-reactive protein (CRP).

All of the ACR-approved measurement tools feature one or more of these elements. For example, the Clinical Disease Activity Index (CDAI) combines a joint count, a patient’s self-assessment on a scale of 0 (very well) to 10 (very poor), and the provider’s assessment of the patient’s status (also using a scale from 0 to 10). These data are plugged into a formula, which produces a number between 0 and 76. A score of 0 to 2.8 means the patient is in remission. Low disease activity is indicated by a score of 2.9 to 10, while 10.1 to 22 suggests moderate activity. A score over 22 indicates high disease activity.

The five tests the ACR favors for assessing disease activity are the CDAI, the 28-joint Disease Activity Score (DAS28-ESR/CRP), Simplified Disease Activity Index (SDAI), Routine Assessment of Patient Index Data 3 (RAPID3) and Patient Activity Scale-II (PAS-II). For measuring functional status, ACR recommends the PROMIS physical function 10-item short form (PROMIS PF10a), the HAQ-II and the Multidimensional HAQ.

All of the ACR-recommended tests share a few things in common, says rheumatologist Lisa Gale Suter, MD, a professor of medicine at the Yale University School of Medicine and a coauthor of the ACR recommendations for disease activity and functional status measures. “They are all scientifically robust and flexible enough to be used at the point of care,” says Dr. Suter. That is, each test has been proven accurate and reliable in clinical studies. And each is simple and fast enough for a doctor to use to make treatment decisions during a 15-minute appointment.

What’s more, adds Dr. England, all ACR-recommended tests include the patient’s own self-evaluation. “It’s important for them to know that we’re not just squeezing their joints and saying how active we think their RA is,” says Dr. England. “We want to listen and have the patient tell us how they’re feeling.”

How T2T Works

Both Dr. England and Dr. Suter use the CDAI tool to track how patients are responding to treatment. Typically, new patients undergo baseline testing, then have their disease activity reevaluated every few months to determine whether a change in therapy is warranted. The interval between office visits can stretch if the patient is doing well, however.

“If a patient is consistently in remission and we haven’t been needing to make any treatment changes, we probably don’t need to see them as frequently,” says Dr. England. What’s more, some patients who are consistently in remission may be able to shift into what Dr. Suter calls “maintenance therapy,” meaning their inflammation is controlled with fewer or less-potent medications. The results of functional assessments can guide other decisions, such as whether a patient might benefit from assistive devices or is experiencing side effects from therapy, says Dr. Suter.

The coronavirus pandemic added a twist to using T2T tools to help patients achieve remission, because many hospitals and clinics temporarily swapped office visits for video conferencing and phone sessions. While many of her patients have resumed in-person checkups, some still prefer telehealth visits, says Dr. Suter. “That has made it even more important to ask really detailed questions about disease activity, because I can’t touch their joints,” she notes.

Drs. Suter and England were also co-authors of an advisory to physicians on using T2T tools during the pandemic. Recommendations downplayed lab tests (because some patients were leery of getting blood drawn) and using other tools instead to aid telehealth visits, such self-evaluation surveys filled out prior to check-in and delivered via patient portals.

Although the goal is to have all RA patients managed using T2T, says Dr. Suter, rheumatology providers in the ACR’s national patient registry are collecting disease-activity assessments only about 60% of the time. If your doctor isn’t yet using T2T tools to set goals and monitor your progress, he or she might start soon, because Medicare and other payers are increasingly requiring clinicians to measure disease activity and functional status as part of routine care.

“You can also ask your clinician, ‘How can I monitor myself?’” says Dr. Suter. “‘Are there ways I can update you if things change?’” Apps for smartphones and tablets (such as Cliexa-RA) are available for collecting data that could help you hit your target, she adds.

Published 6/7/2021


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