Scientists developed a microsimulation model to evaluate the effectiveness of pharmacogenomic testing for adult patients in British Columbia, with newly diagnosed moderate to severe major depressive disorder (MDD). The model predicted that testing could result in 37% fewer patients developing refractory depression, 15% more time of patients feeling well, and a health system cost-savings of $956 million CAD over 20 years.
“Our study shows that, if pharmacogenomic testing guides the prescription of an effective antidepressant, it can reduce the lengthy trial-and-error process many patients experience and dramatically reduce the financial burden on the health care system,” Shahzad Ghanbarian, PhD, the lead author and a research analyst at the University of British Columbia’s Centre for Clinical Epidemiology and Evaluation, Vancouver, said in an interview.
“The next step should be developing implementation strategies and identifying the most suitable health care professionals to provide pharmacogenomic-guided care,” she said.
The study was published online on in the Canadian Medical Association Journal.
Developing a model
The World Health Organization has predicted that depression will be the leading cause of disability worldwide by 2030. However, about half of patients don’t respond to the antidepressant that they are initially prescribed, and more than one-quarter report adverse effects. Previous studies have found that up to 42% of the lack in response stems from genetic factors that affect medication metabolism.
Pharmacogenomic testing, which uses a blood, saliva, or buccal swab sample, could help identify genetic variants involved in drug metabolism and response as well as guide prescribing and reduce adverse effects, the authors wrote.
Dr. Ghanbarian and colleagues developed a microsimulation model in collaboration with patient partners, clinicians, and the health system to evaluate the effectiveness and cost-effectiveness of pharmacogenomic testing for adult patients with MDD in British Columbia. The model included unique patient characteristics, such as metabolizer phenotypes, and followed the experience of patients through diagnosis, treatment, and recurrence.
According to British Columbia administrative data from 2015 to 2020, the model simulated a population of 194,149 adults and incorporated 40 different antidepressants and other treatments, including electroconvulsive therapy (ECT) and psychotherapy. The research team compared treatment pathways for patients with and without pharmacogenomic testing over 20 years.
Overall, the model showed that pharmacogenomic-guided treatment resulted in higher remission rates and lower discontinuation rates, with 23,216 (37%) fewer patients developing refractory depression and decreased use of resource-intensive treatment options such as ECT and psychotherapy (by 28% and 22%, respectively). According to the model, these reductions would save the British Columbia health system $4,926 CAD per patient, or about $56 million CAD over 20 years.
These findings provide a solid economic justification for clinical implementation of pharmacogenomic-guided depression treatment in Canada.
In addition, the model found that patients who underwent pharmacogenomic testing spent 15% more time in the “well” state without depression symptoms and 18% less time in the MDD state with recurrent episodes or refractory depression. In turn, this would mean 1,869 fewer deaths and 21,346 fewer all-cause hospital admissions over 20 years.
Pharmacogenomic testing also led to gains of 0.064 life-years and 0.381 quality-adjusted life-years per patient, or 12,436 life-years and 74,023 QALYs for all of British Columbia over 20 years.
From a cost perspective, the $121 million CAD cost of pharmacogenomic testing and $524 million CAD increase in episodic care were offset by a decrease in the cost of refractory MDD care. In sensitivity analyses, up-front investment in pharmacogenomic testing was typically offset after 2 years through lower direct medical costs, and it was also considered a cost-saving measure from that point forward.
“By incorporating the perspectives of patients with lived and living experience into this model, alongside robust data sets, we were able to carefully simulate the treatment journey of people with major depression,” Dr. Ghanbarian said. “The simulation model is designed to be flexible and could be applied to other jurisdictions beyond British Columbia, where we might expect to see similar benefits, particularly within a comparable Canadian context.”