Genetic testing could help patients with depression: UBC study

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New research from the University of B.C. shows that a type of genetic testing could benefit patients with depression, and aid physicians in prescribing the most effective medications.

The bottom line could be better outcomes for patients with major depressive disorders, and substantial savings for provincial health, said Dr. Shahzad Ghanbarian, lead author of the study and a researcher and health economist at UBC’s centre for clinical epidemiology and evaluation.

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Linda Riches, 67, was one of three patients who took part in the study, was prescribed at least a dozen antidepressants, starting in her 30s, but they failed to help. Her depression affected her work as a teacher, and her family life. Years went by before one medication turned out to be the right fit.

“If you’ve been off because of a mental health issue, people just don’t want to talk about it. So they ignore it. Nobody wants to come and say, ‘Is there anything I can do to help you?’” she said from her home near Prince George.

Only 40 to 60 per cent of patients respond to the antidepressant initially prescribed, said Ghanbarian.

“Around 27 per cent of patients experience side effects they can’t tolerate, including side effects that lead to hospitalization. If their condition wont get better, they try another one, and another one. Eventually they may give up. It’s frustrating for the patient, and challenging for the prescriber,” said Ghanbarian.

According to the study published in the Canadian Medical Association Journal, pharmacogenomic testing, which analyzes how your body metabolizes medications, could save the health system $956 million over 20 years.

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“Until now, there has been a lack of evidence in terms of cost effectiveness. This is comprehensive data,” said Ghanbarian. The study used mathematical modelling to look at 200,000 simulated patients.

The data suggests pharmacogenic-guided treatment is associated with a 37-per-cent reduction in treatment-resistant depression.It could also save patients the process of trial and error as they work with their treatment provider to get symptoms under control.

“A unique element of our model is that it is drug-specific, thereby incorporating most prescribed antidepressants in Canada,” said Ghanbarian, who recently presented the findings at the International Congress of the EuropeanSociety of Pharmacogenomics.

Pharmecogenomic testing, uses a simple saliva test, or cheek swab to look for genes that determine how a person metabolizes a specific medication, and can help determine more precise dosages.

Based on the genetic profile, it would be easy to see if the patient has a genetic predisposition to metabolize quickly or slowly, whether the  the concentration of a medication in the body could be higher or lower, said Ghanbarian.

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The testing is already in use in some jurisdictions for a variety of illnesses to determine the likelihood of a medication working or causing serious side effects, including Tamoxifen for breast cancer, Abacavir for HIV, and some blood thinners.

Pharmacogenomics testing in B.C. is not covered by the public health system, but is available commercially.

On their website, the Ministry of Health said they are examining clinical adoption of the testing, and looking at its economic benefits and utility.

The World Health Organization estimates that five per cent of the global population suffer from depressive disorder, and it is the leading contributing factor to disability worldwide. One out of 10 Canadians will experience depression in their lifetime.

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— with files from CP

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