A new study has found that patients with psoriasis who were treated with biologics were more likely to develop psoriatic arthritis (PsA) than those treated with phototherapy, oral therapy, or no therapy at all, although the authors cautioned readers to consider potential biases when reviewing their findings.
“We do not suggest that these results should be interpreted causally; in other words, biologics likely do not cause PsA,” Elana Meer of the University of Pennsylvania, Philadelphia, and coauthors wrote. The study was published in Annals of the Rheumatic Diseases.
Three studies in dermatology clinic-based populations published this past summer – one from Italy, one from Argentina, and one from Israel – suggested that biologics can decrease a psoriasis patient’s risk of developing PsA. To further assess the impact of treatment with biologics, Ms. Meer and associates retrospectively examined the health records of thousands of patients with psoriasis between the ages of 16 and 90 who were initiating therapy. All told, data from 193,709 patients with psoriasis and without PsA who were treated between 2006 and 2017 were gathered from the OptumInsights Electronic Health Record Database.
A total of 14,569 patients from that cohort initiated biologic therapy while 20,321 patients initiated either oral therapy or phototherapy. The mean age in the biologics group was 45.9 years, compared with 49.8 years in the oral and phototherapy group.
The incidence of PsA across all patients was 9.75 cases per 1,000 person-years, compared with 77.26 among the biologic group, 61.99 among the oral therapy group, 26.11 among the phototherapy group, and 5.85 among those who did not receive therapy. After a multivariable adjustment in which biologics were a time-varying exposure, receiving biologics was associated with a higher incidence of PsA (hazard ratio, 4.48; 95% confidence interval, 4.23-4.75). In a model where time starts at the first use of biologics, the incidence was lower – but still notable – after multivariable adjustment (HR, 2.14; 95% CI, 2.00-2.28) and propensity score matching (HR, 2.17; 95% CI, 2.03-2.33).
Bias likely plays a large role in retrospective PsA study
“We’ve been struggling for the last several years to find a database that allows us to really address this question retrospectively,” study coauthor Christopher T. Ritchlin, MD, of the University of Rochester (N.Y.), said in an interview. “It looks like the model you use for a retrospective analysis heavily influences what you come out with.”
Dr. Christopher T. Ritchlin
He described the potential biases they identified, including the possibility of protopathic bias indicating that patients being treated with biologics who then report joint pain have developed PsA – and are coded accordingly after visiting a rheumatologist.
“This has convinced us that you have to do a prospective study,” he said. “We’ve known that there were flaws with previous studies in this area. We tried to overcome them with our methodology, but there’s no way you can overcome a coding issue when you’re looking at such a large database.”
He noted another likely bias: The patients who are more likely to develop PsA are the ones with severe psoriasis, and they are also the patients most likely to be prescribed biologics.
Courtesy Dr. Joel M. Gelfand
Dr. Joel M. Gelfand
“In my clinical experience, I have seen many patients develop psoriatic arthritis while on biologics for their psoriasis,” coauthor Joel M. Gelfand, MD, of the University of Pennsylvania, added in an interview. “Currently, we do not have adequate data to recommend treating psoriasis with a particular modality in order to prevent psoriatic arthritis. This question, however, is very important to patients and clinicians and ultimately is best answered with a large-scale pragmatic trial.”
Dr. Ritchlin reported that a prospective study in which “patients with psoriasis who do not have arthritis but do have certain risk factors and abnormal findings on musculoskeletal ultrasounds” will be treated with either biologic agents or placebo is about to begin, with a goal of “either attenuating or preventing the onset of PsA.”
The authors recognized their study’s additional limitations, including electronic health records being used as the primary data source and the possibility that medications were prescribed but never filled. That said, they did attempt to address the latter by using two prescriptions for a given therapy as the primary analysis, “suggesting a refill was initiated.”
The authors said that no commercial entities provided support for the study. Two of the authors acknowledged receiving funding from the National Psoriasis Foundation, and several authors declared potential conflicts of interests that included consulting and receiving honoraria from various pharmaceutical companies.