Three experts discuss measurement of outcomes for psoriatic arthritis management and what a “successful” treatment looks like.
John Tesser, MD: Let’s talk about successful outcomes and maybe measures of successful outcomes. What are our goals in treating patients? Let me frame this in the context of how we view or have measured rheumatoid arthritis. That has been an ongoing battle and a challenge for rheumatologists for decades: measuring rheumatoid arthritis using either the Disease Activity Score, the Clinical Disease Activity Index, RAPID3 [Routine Assessment of Patient Index Data 3], some of those, all of those, none of those. We appreciate very much that the ACR20 [American College of Rheumatology 20% improvement], ACR50, and the ACR70 improvement criteria—which are used in judging success in clinical trials—are not used at all in clinical practice. It’s a composite measure of many things, but that measure in and of itself doesn’t identify how much inflammatory disease a person has at any given point in time.
In psoriatic arthritis, interestingly enough, ACR20, ACR50, and ACR70 in clinical trials are utilized as the measure of success for FDA approval for psoriatic arthritis trials. It’s not the only thing that’s measured, but the ACR20 is used as the lowest bar for approval. The CDAI [Clinical Disease Activity Index] is beginning to be used by some people.
But there’s another measurement that’s analogous to the ACR composite criteria. It’s called the minimal disease activity index. It comprises similar things to what’s in the ACR criteria, like how many tender and swollen joints and what’s the patient’s global and pain, functionality, and acute phase reactant—this kind of thing. It’s all put together, and if you measure these things on your patient, then you assign certain points to these things. If the patients meet many points, they’re identified as having low disease activity; even more points, very low disease activity. That measure exists. It has begun to be used in clinical trials. Nehad, do you think this is going to have any utility in clinical practice? What do you do in your practice in terms of identifying outcome measures? When you think you’ve achieved success, how do you assess it?
Nehad Soloman, MD: For a long time, we grappled with this, or at least I grappled with this: what do I use as an outcome measure? Just like with the drugs, we borrowed things from the rheumatoid arthritis experience. When you mentioned the ACR levels, you also mentioned CDAI.The easiest thing to do was obviously the CDAI, which measures tender and swollen joints and assessment both by physician and patient in terms of global experience. But when you think about minimal disease activity index, it also measures tender joints, swollen joints. It looks at the skin, body surface area, and PASI [Psoriasis Area and Severity Index]. It looks at visual analog scales from a pain perspective as well as a global perspective. Then it also looks at the HAQ [Health Assessment Questionnaire] and it adds the other critical point, which we do clinically but we don’t quantify it by looking at enthesitis or entheseal point tenderness.
Beyond that, as I’ve learned to examine this a bit closer, it’s meeting 5 of 7 areas and having them at a level of 1 or less in some areas, 3 or less if you’re talking about body surface area. But there’s a target at each of these. The challenge, although we do a lot of this in clinical practice, just like the ACR scores, we just don’t quantify it. We say, “There’s an improvement in tender joints or swollen joints, or SED [erythrocyte sedimentation] rate and CRP [C-reactive protein] have improved or have normalized.” That’s the quick and dirty way of saying they’re getting better.
As payers demand and as patients demand a number or a target, we may find ourselves using this. To employ this so that we can inform treatment decisions, the world of IT [information technology] is going to meet medicine once more and find a way to make itself into our EHR [electronic health record] in a manner that’s simple. If just like in our EHR, we can quickly insert these, whether part of it is imported from the patient questionnaire or part of it is actively recorded as we’re seeing the patient, then it may very well become more mainstream. But it will be years down the line when we can get this to be streamlined in the EHR.
John Tesser, MD: Those are very good points. I find it very interesting that this particular composite measure, as opposed to the ACR, does identify a certain amount of disease. But psoriatic disease is difficult because there are many domains. It’s not so easy to incorporate all these things into 1 overall grouping. It’s a fairly reasonable attempt, and perhaps over time we’ll use it more and more.
This transcript has been edited for clarity.