More Severe Psoriasis Linked to an Increased Risk of PsA

Doug Brunk

September 30, 2021

The risk of developing psoriatic arthritis (PsA) may increase as the severity of psoriasis increases, results from a large analysis of U.S. medical records demonstrated.

Factors that predict the development of psoriasis in patients with psoriasis include nail, inverse, and scalp psoriasis; family history of PsA; as well as severity of skin disease. And like psoriasis, "PsA is associated with a multitude of comorbidities, including cardiovascular disease, metabolic syndrome, Crohn's disease, obesity, diabetes, uveitis, anxiety, and depression, with correspondingly higher healthcare utilization and direct healthcare costs," wrote corresponding author Joseph F. Merola, MD, MMSc, and colleagues. The study was published online in the Journal of the American Academy of Dermatology. "Timely and accurate diagnosis of PsA is important for improved patient outcomes and appropriate disease management and may prevent prolonged inflammation that leads to structural joint damage and worsening physical function," they added.

The mean time of onset of PsA among patients with psoriasis who develop PsA is 10 years after the first signs of psoriasis appear. An estimated 20%-30% of patients with psoriasis have a concurrent diagnosis of PsA, and the annual incidence of PsA has been reported to be 2.7 cases per 100 patients with psoriasis. While previous studies have suggested that a higher incidence of PsA is associated with greater disease severity, there are limited data in the United States on the topic.

For the study, Merola, a dermatologist and rheumatologist who directs the Center for Skin and Related Musculoskeletal Diseases at Brigham and Women's Hospital, Boston, and his colleagues drew from the Optum EHR database to identify adult patients newly diagnosed with psoriasis between Jan. 1, 2009, and March 31, 2019. Patients diagnosed with psoriasis or PsA prior to the index date were excluded from the analysis for evaluation of incidence but included for evaluation of prevalence. The patients were followed from the index date until the earliest PsA event, death, or end of study or follow-up, whichever came first. The researchers calculated the incidence of PsA among adults with psoriasis as the number of incident PsA events divided by the number of patient-years (PY) at risk, which was reported as the raw incidence per 100 psoriasis PY. They calculated the prevalence of PsA among adults with psoriasis as "the number of prevalent PsA events divided by the number of eligible patients with [psoriasis] and reported by years in the follow-up period," which was a median of 3.7 years.

A total of 114,868 patients were included in the analysis. At baseline, their mean age was 54 years, 53% were female, 89% were White, and 39% were obese. Most patients (102,553) were on nonsystemic agents during the year after their psoriasis diagnosis, while 6,345 were on nonbiologic systemic therapies (NBSTs) and 5,970 were on biologics. The researchers classified patients as having mild psoriasis if they were taking nonsystemic agents, moderate disease if they were taking NBSTs, or severe disease if they were taking biologics.

The overall incidence rate of PsA was 2.9 events per 100 PY and increased by severity of disease. When calculated by severity, the incidence was 2.1 events per 100 PY for patients with mild psoriasis, 9.9 events per 100 PY for those with moderate psoriasis, and 17.6 events per 100 PY for those with severe psoriasis.

When the researchers excluded patients diagnosed with PsA up to 1 year after being diagnosed with psoriasis, the overall incidence was lower (1.7 events per 100 PY), with similar trends for categories of treatment severity. Specifically, the incidence was 1.5, 3.1, and 4.7 events per 100 PY among those with mild, moderate, and severe psoriasis, based on their treatment groups, respectively.

Among the 120,523 patients with psoriasis who were eligible for the assessment of prevalence of PsA, the overall 5-year prevalence of PsA was 14.2% and rose with severity of disease: 9.9% in patients with mild psoriasis, 35% in patients with moderate psoriasis, and 54.9% in patients with severe psoriasis.

Other predictors of PsA onset for both index-date cohorts included weight of 90 kg or greater, female gender, age group 25-65 years (compared with the age group over 65 years), and rheumatic risk factors such as wrist pain and unspecified rheumatism.

"To ensure timely diagnosis and treatment for management and prevention of PsA, patients with [psoriasis] should be routinely screened, especially those with more severe disease and other PsA risk factors," the authors advised.

Merola and colleagues acknowledged certain limitations of their analysis, including the potential for selection bias and its reliance on EHR data which "lacked clinical measures of disease severity such as the PASI, and data on BSA were not available for all study participants; therefore, treatment groups were used as a surrogate for disease severity," they wrote. "As a result, some patients may have been miscategorized, especially patients with severe disease who were untreated."

The study was sponsored by Novartis. Merola disclosed that he is a consultant and/or investigator for Merck, AbbVie, Dermavant, Eli Lilly, Novartis, Janssen, UCB, Celgene, Sanofi, Regeneron, Arena, Sun Pharmaceuticals, Biogen, Pfizer, EMD Serono, Avotres, and LEO Pharma. Four authors are Novartis employees, or employees of a consulting company that provides services to Novartis; and another author disclosed serving as an investigator or consultant for several pharmaceutical companies, including Novartis.

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