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Placebo rates are rising at a similar rate as the recruitment of participants in less affluent countries. A systematic review supports the hypothesis that globalization of recruitment significantly contributes to the higher placebo rates observed in recent psoriatic arthritis (PsA) clinical trials.
“Placebo response rates in PsA trials have been on the rise over the past decades,” said Dr. Andreas Kerschbaumer, from the Medical University of Vienna, in Austria1-3. ACR20 responses in placebo groups can reach up to 43%2. Dr Kerschbaumer added that this increases recruitment pressure on sponsors and investigators3. The study he presented aimed to quantify the change in placebo response rates over time in randomized controlled trials (RCTs) of targeted PsA therapies.
A systematic review was performed of all placebo-controlled RCTs of disease-modifying antirheumatic drugs in patients with PsA, with established background therapy and with ACR20 response rate as an outcome measure. The researchers included 51 studies conducted between 1996 and 2019. The authors observed an increasing ACR20 response in placebo groups, rising by 0.9% each year (95% CI 0.6–1.2; P<0.001). In addition, they saw normalized per capita gross national income (GNI) decrease by -1,124 international dollars a year (95% CI -1,416 to -832; P<0.001). The study’s main result was a strong and significant association between increasing ACR20 placebo responses and the decrease in a study’s gross national income. The estimated ACR20 response decreased by 5.2% (95% CI -7.4 to -3.0; P<0.001) for every 10,000 international dollars.
The authors argue that limited access to healthcare in less affluent regions might lead patients to enroll in trials, potentially amplifying regression-to-the-mean effects and inflating placebo responses. The implications of these findings are the need for equitable healthcare access and adapting strategies for trial designs to address geographical differences and ensure the validity of PSA clinical trial outcomes.
Medical writing support was provided by Michiel Tent
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