Psoriatic Arthritis: What Defines Minimal Disease Activity?

Here’s what you should know — and why you should care — about minimal disease activity in psoriatic arthritis.

Minimal Disease Activity Defined

For many diseases, there is a concept of remission — meaning your disease is well controlled or no longer active. There’s no easy way to define remission for psoriatic arthritis, since it can affect different areas of your body in different ways.

“The challenge of psoriatic arthritis is that it’s a bunch of disparate symptoms, so remission may mean a lot of different things,” says Eric Ruderman, MD, a rheumatologist at Northwestern Medicine in Chicago. “So that’s the idea behind minimal disease activity. It’s akin to remission, but encompasses all the different manifestations of the disease.”

• Tender joint count of 1 or below
• Swollen joint count of 1 or below
• Psoriasis area and severity index of 1 or below, or body surface area of 3 percent or below
• Patient pain visual analog score (VAS) of 15 or below
• Patient global disease activity VAS of 20 or below
• Health assessment questionnaire (HAQ) disability index of 0.5 or below
• Tender entheseal points (where tendons and ligaments connect to bones): 1 or below

In practice, “MDA gives clinicians and patients a practical ‘dashboard’ to ask: Is the disease quiet enough?” says M. Elaine Husni, MD, MPH, a rheumatologist and the director of the Arthritis and Musculoskeletal Center at Cleveland Clinic in Ohio. “MDA captures what patients feel — pain, function, and global disease burden — not just what physicians see.”

Why Minimal Disease Activity Matters

Minimal disease activity gives a picture of your overall disease control right now, and can be used to help make treatment decisions. It may also help predict certain long-term health outcomes in psoriatic arthritis.

“When you pick your drug, you want to say: How close have we gotten to fully controlling disease?” says Dr. Ruderman. “It’s a question of finding the medication that works for that patient.”

MDA can also capture how much of a burden your psoriatic arthritis is in your everyday life. “Less inflammation usually means better joint movement, walking, and daily performance,” says Dr. Husni.

Since MDA captures your overall disease burden, it may help predict long-term damage to your joints. “Persistent inflammation can lead to erosions, new bone formation, deformity, and disability,” says Husni.

But studies on the long-term effects of MDA have so far been fairly small and limited in scope. “There’s some evidence that if you achieve MDA you do better in the long run, but I don’t think we have much firm evidence of long-term outcomes,” says Ruderman.

How to Achieve Minimal Disease Activity

For most people with psoriatic arthritis, MDA is a worthwhile goal of treatment. “It is specific, measurable, and patient-centered,” says Husni.

It’s important, Husni says, to assess the components of MDA regularly and adjust therapies as needed if the person’s treatment goals aren’t being met. This process should involve discussions with your rheumatologist about what you’re looking to get out of your treatment plan.

Steps you can take that may help guide you toward minimal disease activity include:

• Taking medications as directed, or telling your doctor if you need to stop taking a drug because of side effects
• Clearly describing your symptoms, and how they affect your life, to your doctor
• Learning about treatment options and lifestyle measures for psoriatic arthritis
• Bringing up the idea of trying different therapies if your current treatment isn’t working well enough

In some cases, MDA may not be the best or main goal of treatment for psoriatic arthritis. “For example, a patient may meet MDA but still have severe psoriasis. One domain is severe even if the total MDA score looks acceptable,” says Husni. In that case, adjusting treatment may be important to reduce skin symptoms.

And the opposite situation is possible, too — someone who hasn’t achieved MDA but doesn’t need or want a major change in their treatment. “There may be a patient who says, ‘I’m so much better. My joints are well controlled, my function is fine, but I have ongoing skin disease and a few swollen joints that don’t bother me a lot,’” says Ruderman.

For some people, MDA may not be an appropriate or realistic goal because they have other forms of arthritis or conditions that limit movement or cause pain. “Treatment goals have to be individualized in these cases,” says Rebecca Gordon, MD, a rheumatologist at UCHealth Cherry Creek Medical Center in Denver. “Some patients may make meaningful progress without strictly meeting criteria for MDA.”

Dr. Gordon also notes that for people whose psoriatic arthritis largely affects their spine or surrounding areas, a disease score developed specifically for arthritis in this area may be more useful than MDA for setting goals or assessing treatments.