Vikas Majithia, MD, on the Difficulties of Diagnosing Psoriatic Arthritis

In this podcast, Vikas Majithia, MD, discusses some of the difficulties rheumatologists encounter when diagnosing psoriatic arthritis, and key indicators of the disease. Transcript below.

Additional Resource:

• Philipose J, Deodhar A. Classification criteria for psoriatic arthritis: CASPAR. Published online June 14, 2012. https://www.rheumatologynetwork.com/view/classification-criteria-psoriatic-arthritis-caspar

Vikas Majithia, MD, is director of the Division of Rheumatology, professor of internal medicine, and director of the Fellowship Program at the University of Mississippi School of Medicine in Jackson, Mississippi.

Podcast Transcript

Announcer:  The content for this topic is independent and is made available with support from Amgen.

Rebecca Mashaw:  Hello everyone, and welcome to another installment of "Podcasts 360," your go‑to resource for medical news and clinical updates. I'm your moderator, Rebecca Mashaw.

Today, we're continuing our special podcast series on psoriatic arthritis with Dr Vikas Majithia, professor of Internal Medicine, Fellowship Program director, and director of the Division of Rheumatology at the University of Mississippi School of Medicine in Jackson, Mississippi.

Dr Majithia will discuss some of the difficulties in diagnosing psoriatic arthritis. We appreciate your joining us today, Dr Majithia. About 7.5 million people in the United States have psoriasis. While the estimates range widely, it's thought that up to 30% of these patients could actually have undiagnosed psoriatic arthritis.

In your clinical experience and in your research, what have you identified as the primary reasons psoriatic arthritis often goes undiagnosed?

Vikas Majithia: It has to be the kind of nature of the disease itself. There is a heterogeneity in the way psoriatic arthritis presents. That brings us to the most difficult conundrum we have when we are trying to diagnose these patients.

Furthermore, there are difficult presentations which also do not fit the common five major groups of presentations. Of course, there is a clear lack of diagnostic biomarker or finding on diagnostic evaluation that can direct us and confirm with significant confidence that this patient has psoriatic arthritis. That leaves us with a lot of confusion and under‑diagnosis in these patients.

RM:  Some clinical features are clear indications that a patient may have psoriatic arthritis, such as the presence of scalp and nail psoriasis, dactylitis, and enthesitis. Are there other less well‑known clinical signs that a rheumatologist should look for in a patient who may have psoriatic arthritis?

VM:  One of the biggest reasons why these patients are not diagnosed is that most of the time these patients are being seen by primary care providers and dermatologists. They don't necessarily understand the meaning of an inflammatory arthritis, dactylitis, and enthesitis, which are the hallmarks of psoriatic arthritis.

These patients, if they complain of arthritis or arthralgia, they are usually labeled as noninflammatory processes because these findings are subtle. They are hard to actually confirm even after a significant amount of training. There is not enough education about them in providers who are the initial point of entry to health care for the patients.

Furthermore, what complicates the picture is that these patients also do not have adequate access to rheumatologists who are much better versed in trying to diagnose these patients. That has to do with workforce shortage and lack of access to rheumatology in general.

Now, I'll jump back to the clinical features. The fact that presence of scalp psoriasis and nail psoriasis in dermatology clinics should automatically be a trigger for looking at psoriatic arthritis as a possibility in these patients. It's not actually well‑understood and known to the majority of dermatologists.

Unless the patients themselves complained of some joint symptoms, these are not very well asked. Beyond the clinical features of dactylitis, it is hard to feel, touch, and confirm that presence unless you have been trained to do that, and that is not easily done.

Other clinical features other than the ones you described are also a patient who has psoriasis and has inflammatory back pain, involvement of distal interphalangeal joints in a minority of these patients. Once they have it, the chances are it could be psoriatic arthritis.

Higher extent of skin involvement also helps suggest that these patients are at a higher risk of developing psoriatic arthritis. When they reach the rheumatologist, I think the findings can be confirmed and are quite clear and should be the potential on making an actual diagnosis of psoriatic arthritis.

There is one more set of clinical features, which is extra‑articular and extra‑dermatological findings such high involvement in these patients who might have an inflammatory eye disease— uveitis, for example —which can also direct toward consideration of an underlying psoriatic arthritis in these patients.

RM:  One of the rheumatologists who helped to develop the CASPAR criteria said they were designed for case definition for inclusion in clinical trials and not for diagnosis in everyday practice. But are these criteria helpful for the rheumatologist who is trying to make a precise diagnosis of psoriatic arthritis? Do you ever apply these criteria in your own practice?

VM:  These criteria are classification criteria which are specifically to find a homogenous population so that we can study this disease and its treatment. These criteria are clearly a huge step forward in classifying the disease.

In rheumatology, as with any other disease state, we are really dependent upon the physician’s decision or gestalt to make the diagnosis.

These criteria help us find what actually is the most common epidemiology of these patients and they direct us towards possibility of a diagnosis if the patient has inflammatory arthritis and does not seem to have a classic rheumatoid arthritis or other common inflammatory arthritis presentation.

I would say that I look at them when I'm seeing those patients, but I do not use them for diagnosis. What we really need is a diagnostic algorithm which can help us diagnose these patients a whole lot better than just a set of criteria that we have.

RM:  What would such an algorithm need to include?

VM:  That's a really good question. A diagnostic algorithm to be successful should have an entry criteria which should be, what is the most common symptom or present thing, information on a patient?

Once they have that, there would be a set of second and third more specifying questions leading to increased specificity. The first entry criteria can provide us with a high sensitivity. Having secondary information with laboratory testing as well as imaging studies can further help us.

As of right now, we do not have a specific biomarker but we do know that a majority of these patients tend to have systemic disease and they tend to have elevated inflammatory markers like sedimentation rate or C‑reactive protein.

Because of presence of those, the suspicion can go higher. Of course, if they have findings on imaging—in particular, MRI is a very sensitive imaging test. MRI can detect subtle enthesitis, subtle dactylitis, and other findings that psoriatic arthritis patients present with and can be used in that particular algorithm.

Plain radiographs can also be used, but those tend to show more advanced disease, both erosions and formation of new bone. They are clearly widely available, so both of those can be part of that algorithm. To be able to utilize and formulate a diagnostic algorithm like this requires a lot of effort and then also validity to actually apply it in the population.

RM:  You mentioned that of course there is no specific biomarker for psoriatic arthritis and that you do use some tests, like for C‑reactive protein and sedimentation rate. Are there any other types of laboratory tests that can be helpful to a rheumatologist trying to get to a specific psoriatic arthritis diagnosis?

VM:  Even with a strong suggestion that a negative serology for rheumatoid factor and anti‑CRP antibody or other is strongly associated with psoriatic arthritis, even then that may be seen in only about 10% or so of these patients.

Other findings are DNAs and other antibodies, but none of them are consistently shown to help us in diagnosis of psoriatic arthritis.

RM:  What other suggestions might you have for your fellow rheumatologists in regard to diagnosing psoriatic arthritis?

VM:  My take would be that it is important to have a high suspicion of the presence of psoriatic arthritis when we have inflammatory arthritis patients who do not fit other diseases.

My other big push would be to actively collaborate with dermatologists in both educating them to try to get these patients into a rheumatologist if there is presence of some of the clinical indications, such as scalp and nail psoriasis, or findings of this psoriasis and if they have inflammatory joint symptoms.

I think that can go a long way in improving the access to these patients and getting them diagnosed earlier.

RM:  We thank you for your time today and for helping to clarify some of the issues that rheumatologists face in diagnosing psoriatic arthritis in their patients. Thank you so much.

VM:  Thanks.

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