Few randomized controlled trials (RCTs) investigating the effects of biologic therapies on psoriasis actually enroll patients who are fully representative of the real-world population, according to study results published in the British Journal of Dermatology.

Researchers from the University of Manchester, United Kingdom, appended data from the British Association of Dermatologists Biologic Interventions Register (n=6790) to individual participant-level data from 2 RCTs (n=2021).  The studies examined the efficacy of ustekinumab to treat psoriasis, with treatment data collected every 6 months for 3 years and annually thereafter.

Patient variables at baseline were evaluated for their association with an RCT. Trial status was the dependent variable in measuring the C-statistic of the multivariable logistic regression model. In the first year, investigators also examined the risk difference in the incidence rate of serious adverse events in the first year and the Psoriasis Area and Severity Index in 6 months after, the effectiveness and safety outcomes were calculated before and after weighting the results.

There was a calculated C-statistic of 0.82 (95% CI, 0.81-0.83) in the multivariable logistic regression model, suggesting a difference between the 2 groups. Patients who were in the randomized controlled trials were more likely to be between the age of 55 and 59 (odds ratio [OR], 1.29; 95% CI, 1.02-1.62) and 60 and 64 (OR, 1.41; 95% CI, 1.09-1.84), have been exposed to a higher number of prior biologic therapies (OR, 2.31; 95% CI, 2.13-2.50), were black (OR, 2.11; 95% CI, 1.26-3.54), and smoke <10 cigarettes per day (OR, 1.41; 95% CI, 1.15-1.73) or >20 cigarettes per day (OR, 1.74; 95% CI, 1.42-2.12).


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Study limitations included the lack of data on inherent lifestyle and genetic variability between the 2 cohorts, which the researchers believe may have influenced the results.

“Our results show that populations of patients with psoriasis in [RCTs] are very different from real-world populations,” the researchers wrote. “This reinforces the notion that randomized controlled trials have a lower external validity than real-world studies, and our results may help clinicians interpret and explain the differences in safety outcomes between trial results and real-world clinic.”

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Reference

Yiu ZZN, Mason KJ, Barker JNWN, et al; BADBIR Study Group. A standardisation approach to compare treatment safety and effectiveness outcomes between clinical trials and real world populations in psoriasis [published online March 1, 2019]. Br J Dermatol. doi:10.1111/bjd.17849