Psoriatic Arthritis Detection: Screening Tools for Dermatologists

Joseph F. Merola, MD, MMSc; Alice B. Gottlieb, MD, PhD


September 27, 2021

This transcript has been edited for clarity.

Joseph F. Merola, MD, MMSc: Hi. I'm Dr Joseph Merola. I am an associate professor at Harvard Medical School, and I run our Center for Skin and Related Musculoskeletal Diseases. I am truly delighted to be with my dear friend and colleague, Dr Alice Gottlieb. Alice, I'll let you introduce yourself.

Alice B. Gottlieb, MD, PhD: I'm Alice Gottlieb. Both of us are dermatologists and rheumatologists. I'm a clinical professor and medical director in the Department of Dermatology at the Mount Sinai, Union Square address, part of the School of Medicine at Mount Sinai in New York.

Merola: We have a brief time today to discuss early detection of psoriatic arthritis in patients with psoriasis. We're going to have a little back and forth, and Alice is going to start us off.

I think one of the first questions is to unpack the disease state a bit for the non-rheumatologists, talking about the early signs of psoriatic arthritis and why dermatologists should care about psoriatic arthritis.

Maybe you can take us on a little tour of the disease state, and then we can spend some time on workup and screening.

Gottlieb: The six domains of psoriatic arthritis are peripheral arthritis, axial or spinal disease, enthesitis (inflammation where the ligaments and tendons insert into bone), dactylitis (inflammation of the whole digit), skin manifestations, and nail manifestations.

Why should dermatologists care about psoriatic arthritis? Psoriatic arthritis is the most common comorbidity of psoriasis; in many cases, it's easy to diagnose.

If you make a mistake and you send osteoarthritis or fibromyalgia to the rheumatologist, those patients need treatment, too. If you miss the psoriatic arthritis, then you've done the patient a disservice. Why? Because psoriatic arthritis is potentially disabling.

It is sad that in that setting, it frequently goes underdiagnosed — up to 41% of cases. We have a warning of who's going to get psoriatic arthritis: It's the patient with psoriasis. We have usually a 10- to 12-year warning because cutaneous disease in 84% of patients precedes the joint disease by an average of 10-12 years. Dermatologists can be the first to detect psoriatic arthritis.

Why does it matter? We currently have four tumor necrosis factor (TNF) blockers and two interleukin-17 blockers that inhibit radiographic progression of psoriatic arthritis and are US Food and Drug Administration (FDA)–approved to do so. Dermatologists can prevent disability by initiating treatment early on.

If you're treating psoriasis, it's essential to know whether the patient has psoriatic arthritis. For a patient with mild skin disease, we'll usually use topical treatment. If they have mild skin disease and psoriatic arthritis, we almost always use systemic treatment. The presence of psoriatic arthritis is independent of presenting psoriasis severity. By that, I mean that you can see psoriatic arthritis in people with mild skin disease. You have to ask every patient at every visit about joint complaints.

Merola: We've heard, I think, that it's a common comorbidity. I know you've often said psoriatic arthritis is the most common comorbidity of psoriasis. This obviously matters when it's undiagnosed. Can you comment a bit more on the risk for progression and the risk for damage among patients with psoriasis?

Gottlieb: If a patient has psoriatic arthritis, a delay in diagnosis of over 6 months leads to worse musculoskeletal outcomes — in fact, much worse. It's about an 11-fold risk of having mutilating arthritis, a fivefold risk of having joint erosions, a fourfold risk of having eating up of bone or osteolysis, a twofold risk for sacroiliitis, and so on. We don't want to delay diagnosis.

Merola: That was an awesome review of the disease state. In a moment, we're going to talk about screening and some ways to make it easy for the dermatologists to approach psoriatic arthritis. Some people may think, "Well, I don't really know how to work it up. I don't know the labs to order or what radiology I need." Could you comment on that? Then I think we can start to transition a bit into screening and how to make this easy for the non-rheumatologist to consider.

Gottlieb: First of all, the CASPAR criteria for psoriatic arthritis require that you have an inflammatory musculoskeletal condition, meaning either enthesitis, arthritis, or inflammatory back pain. You need 3 points, and you can have 2 points by having a psoriasis plaque and having nail changes. None of that requires a lab. Of all the other criteria that can give you points, there's only one lab test in there.

I almost never use lab tests to diagnose psoriatic arthritis. The most common x-ray finding in early psoriatic arthritis is a normal x-ray. That is not an obligatory part of screening for psoriatic arthritis.

Dr Merola will tell you ways that the doctor can help screen, but he's also going to show you a way that the patient basically self-diagnoses and gives you a target to let you know whether your treatment is working or not. With that, I will transition to Dr Joseph Merola.

Merola: Thanks, Alice. I'll try to touch on three big topics, and we'll have some discussion surrounding them, as well. We want psoriatic arthritis screening certainly to happen, and it should be done for all of our patients with psoriasis. Alice is part of this effort with the ADA American Academy of Dermatology (AAD) guidelines. Even our AAD guidelines suggest that we should be screening for psoriatic arthritis in all of our patients with psoriasis. Alice, as always, is really a proponent and a champion of this.

In terms of the screening, there are formal screening tools, which I'll share in a moment. There is a screening mnemonic that we put in the literature a couple of years ago called "it's as easy as PSA." Remember "PSA" whenever we see our patients with psoriasis that we're screening for arthritis. The P stands for pain in the joints. We are asking, does the patient have joint pain?

S is for stiffness that occurs after waking in the morning, for example, or after a period of inactivity that lasts 20 or 30 minutes, or more. This is prolonged stiffness that improves with activity. If you can remember a second S, that's for swelling or sausage digit, which refers to the dactylitis that's very specific to psoriatic arthritis and spondyloarthritis disorders.

A is for axial disease, reminding us again that our patients can have spine involvement that is qualified with the same stiffness, improvement of activity, et cetera.

If a patient has two of those three, we should think about performing a formal screening test or referring to a rheumatologist at that point. There are many validated screening tools out there. One that we tend to recommend is the PEST screening tool (the Psoriatic Epidemiology Screening Tool), which is available for free, for example, on the GRAPPA app (the Group for Research and Assessment of Psoriasis and Psoriatic Arthritis). It is a simple five-question tool. If a patient answers "yes" to three or more questions, it's considered a positive screening result and the outcome should prompt either further work-up in the office or a referral at that point.

It's very, very easy. I'll come back to how it can be administered in an easy way, as it's patient-facing. If it's given to a patient while they're in the waiting room or as they're sitting on the exam table waiting for you to come into the room, or even before they come to their visit, it really isn't a burden on the office. We'll come back to that at the end.

In addition to the PEST screening tool, there is a symptom measurement tool called the PsAID, which is a validated psoriatic arthritis symptom measure tool that looks at both disease severity and impact. It is also available for free on the GRAPPA app.

Alice and I, together with a group called IDEOM (the International Dermatology Outcome Measures group), have worked on a framework for the measurement of these symptoms in patients with psoriasis. Our suggestion is that patients receive the PEST screening tool. If it is positive, they should then proceed to the symptom measurement tool.

Very briefly, a score less than or equal to 4 suggests that their musculoskeletal symptoms are in an acceptable state, and a score greater than 4 suggests an unacceptable state. In that case, we would think about co-managing or a referral to a rheumatologist. We could think about changing any therapy that they're already on or modifying therapy. At that visit, we would suggest it might influence our discussion and decisions around treatment options if those are positive.

To recap briefly, there's really an opportunity here for us as dermatologists to be involved in a key comorbidity. It's easy to perform screening, whether it's the PSA mnemonic in the office that leads to the PEST screening tool, which can be done with low burden on the office — it's really a patient-facing opportunity — as well as this PsAID symptom measurement tool.

I'll use that as a transition point as we wrap up our discussion to cover some novel applications of these. We've been talking for some time that because most of our academic and private practices are using an electronic medical record (EMR), there's an opportunity to push these screening tools out to patients before or after a visit. This can be done with low burden.

Alice and her center are championing this effort and doing it, for example, with the Epic EMR system. Maybe we can take 2 minutes before we wrap up, Alice, to comment on some ways we think we can implement this in a practice setting or in an academic setting.

Gottlieb: This has been championed for the whole Mount Sinai system, but starting at Mount Sinai, Union Square, I have a very supportive and innovative management team. Basically, we are talking with the Epic team and the physicians in charge of information and technology, and both PEST and the PsAID are being put into the Epic system. Epic will calculate the scores.

With the patient at home or in the office, on a tablet or through MyChart (which is a patient portal), if there's a psoriasis code associated with their diagnosis, they will be given the PEST. If the PEST is positive, the patient will then be given, with an explanation, the PsAID-12. When the doctor opens the patient's chart, they will see two drop-down items. The first one will give the PEST score and will say that your patient may have psoriatic arthritis and a referral has been made to rheumatology. Obviously, if they come with a diagnosis of PsA, then they won't be given the PEST.

For anybody with a diagnosis of psoriatic arthritis, if the score is more than 4, there will be a drop-down menu, which will list the therapeutic options. It won't tell them exactly which one to pick, but it will list the drugs that are FDA-approved for psoriatic arthritis.

We hope that at no cost of time, really, to the doctor — the patient is doing the work — to screen for and assess psoriatic arthritis, there will be more referrals to rheumatology from those doctors who are not comfortable treating psoriatic arthritis, more early detection of psoriatic arthritis, better control of psoriatic arthritis, and ultimately less disability, with less than a minute of work for the dermatologist.

Merola: Alice, that's wonderful. Hopefully this was helpful in this relatively brief time we've had to cover a lot of ground.

I'll just give us a summary comment. We covered that psoriatic arthritis is a major comorbidity of psoriasis in up to one third of patients, yet it remains underdiagnosed. Alice reviewed the different domains of psoriatic arthritis and the way they clinically present.

We focused on ways to screen that are easy for the physician in and out the office, using the PSA mnemonic, the PEST screening tool, and potentially even measuring symptoms using the PsAID, for example. This leads us to appropriate management, whether it's in the office or through a collaborative model, referring to a rheumatologist.

Thank you for your attention. Alice, it's always a delight to share time with you.

Gottlieb: Thank you.

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