Early identification of axial psoriatic arthritis (axPsA) might be aided by screening people with psoriasis for signs of axial involvement during routine dermatology check-ups, research suggests.
The investigators recommend referral to a rheumatology clinic for adults with a confirmed diagnosis of psoriasis who developed chronic back pain before the age of 45 years that has lasted at least 3 months, and who have not received a biologic or targeted synthetic DMARD in the previous 12 weeks.
The screening questionnaire “is easy to apply and not time-consuming, which makes its application feasible in daily practice ideally in combination with a screening for peripheral disease,” write Theresa Hunter (Eli Lilly and Company, Indianapolis, Indiana, USA) and co-workers in the Annals of the Rheumatic Diseases.
During the study, 42.5% of 355 adults attending 14 dermatology clinics in Berlin, Germany, between October 2019 and January 2020 met the screening criteria for a rheumatology referral.
Of the first 100 consecutively referred patients examined, 14 were diagnosed with axPsA – three of whom had both axial and peripheral involvement – while five patients were diagnosed with peripheral PsA without axial involvement, the researchers report.
Overall, 64.3% of the 14 patients diagnosed with axPsA met the Assessment of SpondyloArthritis International Society classification criteria for the disease, and only one of the 19 patients did not meet the Classification Criteria for Psoriatic Arthritis.
Compared with adults without PsA, those with axPsA had on average shorter durations of psoriasis (13.6 vs 20.3 years) and back pain (12.2 vs 18.6 years), albeit these differences were not statistically significant.
But Hunter and co-authors note that adults with axPsA had significantly higher disease activity than those without PsA based on the ASDAS (2.9 vs 2.3 points), as well as higher DAPSA scores (mean 17.5 vs 11.2 points).
Adults with axPsA also had a significantly higher average C-reactive protein level (8.0 vs 2.5 mg/L) and were significantly more likely to have a concentration above 5 mg/L (35.7 vs 13.6%).
In addition, researchers say that the “study provided evidence for the important role of imaging (and specifically MRI [magnetic resonance imaging]) in diagnosing axPsA.”
All the patients with axPsA showed active inflammatory and/or structural inflammatory changes in the sacroiliac joints and/or spine on imaging whereas no such changes were detected in any of the patients with peripheral PsA or no PsA.
MRI showed axial involvement in the spine for 35.7% of the axPsA patients, while 37.5% had a radiographic sacroiliitis grade of 2 or higher unilaterally and 28.6% met the modified New York criteria for radiographic sacroiliitis.
The corresponding rates among patients with peripheral PsA or no PsA significantly differed, at 0.0%, 4.9%, and 1.9%, the investigators say.
And the authors note that while all four patients who met the modified New York criteria for radiographic sacroiliitis had active and/or structural inflammatory changes in their sacroiliac joints on MRI, five other patients had sacroiliac joint involvement that was visible only on MRI.
“These findings highlight the importance of MRI in detecting axial involvement in patients with PsA in the absence of definite radiographic changes in the sacroiliac joints,” they write.
Hunter et al conclude: “These results provide valuable real-world insights into the possibility of diagnosing axPsA early with the ultimate goal of improving the care and quality of life of patients living with the disease.”