Comparing Disease Impact and Activity in Psoriatic Arthritis by Ethnic Background

Patients of South Asian (SA) origins who have psoriatic arthritis (PsA) have a worse clinical phenotype and worse disease impact than patients of North European (NE) origins, according to research published in Rheumatology.

The cross-sectional study compared patients of SA and NE origin from 2 hospitals in Northern England. The researchers compared clinical manifestations and impacts of PsA and expected that the SA population would have less disease activity and structural damage but would have disease impact that was similar to that seen in the NE population.

“Ethnicity has been implicated as a factor contributing to differences in disease expression, clinical manifestations and prognosis in SpA [spondyloarthritis] and RA [rheumatoid arthritis],” the authors wrote. “Studies have found that SpA runs a different course in non-white Caucasians, Asians and Africans as compared with White Caucasian populations.”

The study included 58 SA patients, who were mostly first-generation immigrants or born in the United Kingdom with grandparents from northeast Pakistan. In addition, 48 patients of NE origin were recruited. These patients were both in the United Kingdom or had grandparents born in the United Kingdom.

The SA patients had more tender and swollen joints, more severe skin disease, and worse disease activity as measured by the Psoriatic Arthritis Disease Activity Score. While fewer SA patients had enthesitis, they had more severe enthesitis, and the SA population had more patients with dactylitis. There was no difference in Sharp-van der Heijde scores between the groups and the 2 groups had similar time between diagnosis and radiograph (mean 5.3 years for SA patients and 5.2 years for NE patients).

SA patients also had poorer quality of life and function with higher visual analogue scale scores for global and skin. They also had higher scores for the Health Assessment Questionnaire, the PsA Quality of Life tool, and the Ankylosing Spondylitis Quality of Life tool. SA patients also had worse scores on the physical function subscale of the 36-item Short Form Health Survey.

“Contrary to our study hypothesis, and based on studies in RA, SA patients had a more severe clinical phenotype and greater impact of disease, yet received similar treatment,” the authors wrote.

Despite the SA patients having a more severe phenotype, both groups used the same treatments, they noted.

“Ethnicity may be an important factor in determining the presentation and management of PsA, but further longitudinal studies controlling for such factors as socio-economic status, smoking, delay in diagnosis and treatment response are needed to further explore these differences,” the authors concluded.

Reference

Aslam T, Mahmood F, Sabanathan A, Waxman R, Helliwell PS. A clinical and radiographic comparison of patients with psoriatic arthritis from different ethnic backgrounds. Rheumatology (Oxford). Published August 10, 2020. doi:10.1093/rheumatology/keaa298