RA Outcome Measures Made Simple (or Not?)

April 15, 2014

HAQ, CDAI, RAPID3, DAS28: Which outcome measure should you use to track progress in patients with rheumatoid arthritis? Here, a brief review of their differences, and the arguments for a new paradigm in disease assessment.

You’re urged to assess outcomes in rheumatoid arthritis (RA). For this, you have an alphabet soup of options.

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Which is best? That's under quiet but continual debate.

Is it time for a new paradigm?

David T. Felson MD MPH, who helped to develop the ACR20, and his colleague Michael P. LaValley PhD, are among the many who think so.

"Not everything that can be counted
counts. And not everything that counts
can be counted." --Albert Einstein

Simpler outcome measures should be developed, they have written, without "arbitrarily characterizing some patients as responders while labeling others as non-responders."1

Do rheumatologists really need to simpilfy the whole process of measuring treatment responses and patient outcomes? Or should the specialty settle on one scale that works best for most patients, and just stick with that?3,4

What do you think? (There's a place for comments below.)

For the purposes of discussion, you may refresh your memory about the translations of the acronyms, and ponder the inconsistencies between them, on the next page.

Keys to the Rheumatologists' Toolbox

Clinical Response Measures

•   The European League Against Rheumatism(EULAR) recommends a simple set of choices based on DAS28 scores:

                 1.  Good
                 2.  Moderate
                 3.  Poor

•   The American College of Rheumatology assessment (ACR20 etc.) counts the percentage of improvement in painful and swollen joints (or in five other core measures: pain, patient and physician global assessments, self-assessed physical disability, and acute phase reactant), resulting in:

                 1.  ACR20
                 2.  ACR50, and
                 3.  ACR70

Both are used in clinical trials, of course. At times, they are at odds with each other.1

Functional Assessments

The most widely used is the Health Assessment Questionnaire (HAQ), consisting of:

             -- Yusuf Yazici, MD

•  Physician Global Assessment (PGA): a binary yes/no clinical evaluation of presence of pain or swelling in any of 13 joints, bilaterally.

•  Patient Global Assessment asks patients to rate pain on a linear scale and to assess their ability to perform everyday tasks (e.g. getting out of bed and getting dressed, sleeping, walking, bathing, and dealing with depression or anxiety), as either:

                1.   no difficulty
                2.   some difficulty
                3.   much difficulty
                4.   unable to do

The Modified HAQ (MHAQ) and the Multi-Dimensional HAQ (MDHAQ) are shorter and easier to use in the clinic, says Yusuf Yazici MD, assistant professor of medicine at the New York University School of Medicine/Hospital for Joint Diseases in New York. "If you're looking solely at function," he adds, "one of these should be our main outcome tool."

There is often discordance between results of the PGA (plus  imaging and lab results) and the patient's responses in the HAQ.2 The crux of the discrepancy, in the words of Edward Keystone MD of the University of Toronto, lead author of many clinical trials in rheumatology, is that "the patient says make me better now. The doc says I have to worry about you today but I also have to worry about you tomorrow  ... The patient doesn’t really appreciate where the doc is coming from."

"A more focused definition is needed," he adds.

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By combining different measures into a single score, composite indices are more reliable in measuring the total impact RA has on the patient. They include:

•  Disease Activity Score for 28 joints (DAS28)

•  Simplified Disease Activity Index (SDAI)

•  Clinical Disease Activity Index (CDAI)

•  Routine Assessment of Patient Index Data (RAPID3)

So how do these measures measure up?

Read about the latest analyses on the next page.

A study published online in February by Josef Smolen MD and coauthors from Vienna compared disease activity levels determined by the SDAI, CDAI, and DAS28, and self-reported outcomes such as functional disability (HAQ scores), health-related quality of life (HQRoL), work productivity and impairment (WPAI), physical component score (PCS), and mental component scores (MCS). They found the highest correlation between disease-activity scores and outcomes of functional disability on the HAQ.5

A recent systematic literature review in Seminars in Arthritis and Rheumatismof swollen and tender joint counts concluded they were not always reliable as an outcome measures, due to a disparity between patient and physician reports.6

A 2013 study in Arthritis Care & Researchfound that patient and physician global assessments often tell completely different stories -- with more patients reporting poorer health status, more pain and fatigue than their rheumatologists recognize.2

Other research indicates that patients’ global assessments are more influenced by pain, while physicians’ assessment is influenced more by swollen and tender joint counts and erythrocyte sedimentation rates (ESR). It has also been suggested

          -- Yusuf Yazici MD

that rheumatologists barely glance at patients’ assessments, giving more weight to objective measures, such as lab resultsand x-rays.2

If the ultimate outcome in RA is disease remission or low disease activity what’s the best way to know if a patient has reached that goal?

“It’s kind of pointless to quibble about which composite score or tool is better, which is more precise, if we should try to come up with new measures,” Yazici concludes. “Everyone has their favorite. They all perform similarly. It’s time to pick one and start using it.”





1.  Felson DT, Lavalley MP. The ACR20 and defining a threshold for response in rheumatic diseases: too much of a good thing. Arthritis Res Ther (2014) 16:101. [Epub ahead of print Jan 2 12014]
2.  Castrejón I, Yazici Y, Samuels J, et al.Discordance of global estimates by patients and their physicians in usual care of many rheumatic diseases is associated with 5 MDHAQ scores not found on the HAQ.Arthritis Care Res (2013) doi: 10.1002/acr.22237. Published online ahead of print.
3.  Yazici Y and Simsek I. Tools for monitoring remission in rheumatoid arthritis: any will do, let’s just pick one and start measuring. Arthritis Res Ther  (2013) 15:104 http://arthritis-research.com/content/15/1/104
4.  Flurey CA, Morris M, Richards P, Hughes R, Hewlett S. It's like a juggling act: rheumatoid arthritis patient perspectives on daily life and flare while on current treatment regimes.Rheumatology (Oxford) (2013) Dec 19. [Epub ahead of print].
5.  Radner H, Josef S Smolen JS, Aletaha D. Remission in rheumatoid arthritis: benefit over low disease activity in patient-reported outcomes and costs. Arthritis Res Ther (2014) 16:R56 doi:10.1186/ar4491.[Published online: 21 February 2014].
6.  Cheung PP, Gossec L, Mak A, March L. Reliability of joint count assessment in rheumatoid arthritis: A systematic literature review. Semin Arthritis Rheum (2013) Nov 13. pii: S0049-0172(13)00246-1. 10.1016/j.semarthrit.2013.11.003. [Epub ahead of print]
7.   Studenic P, Radner H, Smolen JS, Aletaha D. Discrepancies between patients and physicians in their perceptions of rheumatoid arthritis disease activity. Arthritis & Rheumatism (2012) 64:2814–2823. doi: 10.1002/art.34543.