Body Surface Area of Psoriasis Strongly Predicts Psoriatic Arthritis Risk

Researchers examined the association between psoriasis severity and the development of psoriatic arthritis.

Body surface area (BSA) affected by psoriasis, along with obesity and depression, can be used to predict risk of developing psoriatic arthritis (PsA), according to study results published in Rheumatology.

It is known that the early identification of PsA, though important in improving outcomes, is challenging for clinicians. Assessment of psoriasis may be helpful as most patients with PsA have a history of psoriasis.

The objective of the current prospective population-based cohort study was to assess the risk for PsA based on psoriasis severity and other factors that are associated with PsA development, including obesity and depression.

Patients aged between 25 and 60 years with psoriasis were randomly selected from The Health Improvement Network, a large population-based health database in the United Kingdom, between 2008 and 2011. Questionnaires were sent to patients’ general practice providers to determine the approximate BSA of psoriasis, measured using the Patient Report of Extent of Psoriasis Involvement (PREPI) tool. The BSA categories were less than 3% (mild), 3% to 10% (moderate), and more than 10% (severe). The cohort was followed up with prospectively for incident cardiovascular disease and PsA.

Among 8881 patients (49% women) with psoriasis and available BSA data, 52% had mild, 36% had moderate, and 12% had severe psoriasis. The incidence of PsA was 5.4 cases per 1000 person-years over a mean follow-up period of 4.2 years.

Multivariate analysis adjusted for age and sex showed that severe BSA (hazard ratio [HR], 2.01; 95% CI, 1.29-3.13), moderate BSA (HR, 1.44; 95% CI, 1.02-2.03), obesity (HR, 1.64; 95% CI, 1.19-2.26), and depression (HR, 1.68; 95% CI, 1.21-2.33) were associated with incident PsA.

Limitations of the study included a small number of risk factors tested, reporting of BSA by general practitioners instead of dermatologists, detection bias because patients with obesity and depression are more likely to see their general practitioners more often, a limited follow-up time period, and lack of consideration for psoriasis treatment.

The researchers concluded, “This study demonstrates that a combination of relatively common risk factors can be used to approximate risk for PsA in patients with psoriasis in primary care clinical practice. These data inform which patients may be at highest risk for PsA such that a patient’s presentation with joint complaints may warrant further work-up for inflammatory arthritis. Furthermore, these data suggest that there is an opportunity to identify patients with PsA earlier and open the opportunity for interventions targeting prevention of PsA. Additionally, these data underscore the importance of both obesity and depression, treatable conditions, in patients with psoriasis.”

Disclosure: Some study authors declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of disclosures.


Ogdie A, Shin DB, Love TJ, Gelfand JM. Body surface area affected by psoriasis and the risk for psoriatic arthritis: a prospective population-based cohort study. Rheumatology. Published online September 11, 2021. doi:10.1093/rheumatology/keab622