The use of ultrasound in screening for psoriatic arthritis in patients with psoriasis could reduce the number of unnecessary referrals to rheumatologists, according to a research letter published in the British Journal of Dermatology.
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Up to one-third of patients with psoriasis have underlying psoriatic arthritis (PsA), but half of all patients with psoriasis experience nonspecific musculoskeletal complaints.
“Different screening tools have been developed for the dermatology practice to distinguish patients with a higher likelihood of having PsA; however, the low specificities of these tools limit their use in clinical practice,” wrote Dilek Solmaz, MD, and colleagues at the University of Ottawa.
In this prospective study, 51 patients with psoriasis were screened for referral to a rheumatologist using the Early Arthritis for Psoriatic Patients and Psoriasis Epidemiology Screening Tool questionnaires. They also underwent a limited ultrasound scanning of wrists, hands, feet, and the most painful joint, which was reviewed by experienced rheumatologists.
A dermatologist was asked to make a decision on referral based on the questionnaire data alone, then invited to revisit that decision after viewing the ultrasound results. When basing their decision on the questionnaires only, the dermatologist decided to refer 92% of patients to a rheumatologist. Of these patients, 40% were subsequently diagnosed with PsA, which represented a sensitivity of 95% but specificity of just 9%.
After reviewing the ultrasound data, the dermatologist revised their recommendations and only referred 43% of patients. Of these, 68% were later diagnosed with psoriatic arthritis. Among the patients who were not referred after the ultrasound review, five were diagnosed with PsA, but two had isolated axial involvement with no peripheral joint disease. Excluding these two cases, the sensitivity decreased to 88% but specificity increased to 77%.
“Screening tools in psoriasis that have high sensitivities usually have low specificities, which means a higher number of patients to be referred to rheumatology than needed,” the authors wrote. “Our study demonstrated that a musculoskeletal [ultrasound] based on a predefined protocol improves the referrals made to rheumatology.”
The authors did note that the ultrasounds were reviewed by experienced rheumatologists, so the results might not be generalizable to less-experienced sonographers without experience in musculoskeletal disorders.
The study was funded by AbbVie. One author declared receiving funding for a fellowship from UCB. Two authors declared honoraria and advisory consultancies with the pharmaceutical sector, including AbbVie.
SOURCE: Solmaz D et al. Br J Dermatol. 2019 Nov 28. doi: 10.1111/bjd.18515.