Making Psoriatic Arthritis Harder to Miss


At its 2014 annual meeting, GRAPPA continues development of criteria to help non-rheumatologists spot psoriatic arthritis.

Many general practitioners miss psoriatic arthritis (PsA), because it shares features with other forms of inflammatory arthritis. Dermatologists may overlook it, being unaware of the connection between psoriasis and PsA, and even rheumatologists may not observe that a PsA patient also has psoriasis.

The Group for Research and Assessment of Psoriasis and Psoriatic Arthritis (GRAPPA) is working on clinical criteria to distinguish PsA -- and its inflammatory manifestations like dactylitis and enthesitis -- from non-inflammatory arthritis. That effort took the spotlight as GRAPPA’s 2014 annual meeting got underway in New York July 10.

Primary care physicians aren’t trained to identify inflammatory arthritis (IA). “Dermatologists may also lack confidence in identifying PsA, which requires the presence of enthesis or spondyloarthritis in their psoriasis patients," remarked GRAPPA criteria committee chair Philip J. Mease, MD, director of rheumatology research at the Swedish Medical Center in Seattle and a clinical professor of medicine at the University of Washington.

Mease pointed to a 2013 study he led involving 959 patients diagnosed with plaque psoriasis at dermatology clinics in the US, Canada, and Europe. It found that only 30% (n=285) received a correct diagnosis of PsA.1  At the same time, 5% of those previously diagnosed with PsA had been misdiagnosed.

Among the study group, nearly half of the patients (n=117, or 41%) were unaware they had PsA.

While confirming the estimated prevalence of PsA among psoriasis patients, he said, the study points up the lack of standardized diagnostic criteria. "Clearly, we need to develop specific criteria to distinguish musculoskeletal inflammation so a correct diagnosis can be made," Mease added. “For example, what questions should non-rheumatologists ask patients to tease out the red flags?”

As a model, GRAPPA is looking to criteria for inflammatory back pain developed by the Assessments in Spondyloarthritis International Society (ASAS). Key elements of these criteria include age of onset before 40, duration of at least 3 months, gradual and insidious onset of pain that improves with activity and worsens after rest (spondylitis), along with enthesitis (pain at bone-tendon insertions) and digital dactylitis.

In seven breakout groups (peripheral arthritis, axial disease, psoriasis, nail disease, dactylitis, enthesitis, and comorbidities, each including patient representatives and dermatologists,) GRAPPA members discussed other ways the ASAS criteria might be expanded. 

Take the key physical sign of joint swelling: Non-rheumatologists need to distinguish the characteristic spongy feel of swollen and inflamed joints in IA from the bony enlargement of osteoarthritis. A 2009 study also found that adding elevated C-reactive protein (CRP) to the mix substantially increases sensitivity.

Other potential elements of PsA criteria:

    -- the presence of autoimmune thyroid disease or type 1 diabetes,
    -- a family history of lupus or rheumatoid arthritis,
    -- skin and scalp lesions,
    -- chronic night pain,
    -- gender (males are less likely to have fibromyalgia, which is important to the differential),
   -- lack of trauma or physical stress in enthesitis, and
   -- symptom duration longer than six months, because many patients can’t pinpoint when their pain began.

Reporting on behalf of his break-out group, William Tillet, BSc, MBChb, MRCP of the Royal National Hospital for Rheumatic Diseases in Bath UK, noted that children present uniquely and it’s important to distinguish between growing pains and inflammatory pain.

Dafna D. Gladman MD, a professor of medicine at the University of Toronto, pointed out the difference between cold and hot dactylitis, with acute, painful, swelling and redness.

The next steps in this process, begun at GRAPPA’s 2012 meeting, are to condense the list of suggested elements, conduct an online survey of GRAPPA members, rank the key elements, and conduct more patient focus groups. Finally the criteria must be validated  globally to insure they are generalizable.

Completing the process will require grant funding, Dr. Mease said, which GRAPPA is actively seeking.



[1] Mease PJ, Gladman DD, Papp KA, et al. Prevalence of rheumatologist-diagnosed psoriatic arthritis in patients with psoriasis in European/North American dermatology clinics. J Am Acad Dermatol. 2013;69(5):729-735. DOI:10.1016/j.jaad.2013.07.023.

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