Pharmacogenetic Testing Options Relevant to Psychiatry in Canada: Options de tests pharmacogénétiques pertinents en psychiatrie au Canada

Abstract

Objective: To identify and assess pharmacogenetic testing options relevant to psychiatry in Canada. Method: Searches of published literature, websites, and Standard Council of Canada’s Laboratory Directory were conducted to identify pharmacogenetic tests available in Canada. Identified tests were assessed on 8 key questions related to analytical validity, accessibility, test ordering, delivery of test results, turnaround time, cost, clinical trial evidence, and gene/allele content. Results: A total of 13 pharmacogenetic tests relevant to psychiatry in Canada were identified. All tests were highly accessible, and most were conducted in accredited laboratories. Both direct-to-consumer and clinician-gated testing were identified, with turnaround times and cost ranging from 2 to 40 days and CAD$199 to CAD$2310, respectively. Two tests were supported by randomized controlled trials. All tests met minimum gene and allele panel recommendations for psychiatry, but no 2 panels were identical. No test was unequivocally superior to all other tests. Conclusions: Pharmacogenetic testing in Canada is readily available but highly variable in terms of ordering procedures, delivery of results, turnaround times, cost, and gene/allele content. As such, it is important for psychiatrists and other health-care providers to understand the differences between the available tests to ensure appropriate selection and implementation within their practice.

How Can Drug Metabolism and Transporter Genetics Inform Psychotropic Prescribing?

“…This variability presents challenges for clinicians and other end users. Maruf et al (2020) suggest the following should be considered: (a) whether or not the lab is accredited; (b) the relevance of the genetic variants to the medications of interest; (c) test logistics (such as turnaround time). With genes such as CYP2D6 that are particularly challenging, a pragmatic approach may need to be taken: balancing a desire for a fast turnaround in a clinically accredited laboratory with a comprehensive coverage of all relevant functional variants.…”

How to Utilize Clinical and Genetic Information for Personalized Treatment of Major Depressive Disorder: Step by Step Strategic Approach

“…CYP2D6 / CYP2C19 genotyping is not available in most clinical services and it is often not reimbursed by national health care systems, therefore if a patient is willing to fund their own genetic testing, commercial pharmacogenetic tests are an option. These tests have a median cost of CAD 499 (range from CAD 199 to CAD 2,310) according to a recent review referred to the tests available in Canada (however, prices may not be the same in other countries) [ 38 ]. When considering this possibility, clinicians should keep in mind that usually commercial pharmacogenetic tests include also genetic variants not endorsed by guidelines [ 39 ], and two main points should be considered to guide the choice: 1) the test has to include all the genetic variants endorsed by guidelines (see [ 32 ]), pay particular attention if the patient is of non-European ancestry, as the frequency of variants in CYP2D6 / CYP2C19 genes varies across ethnicities, sometimes of a great extent [ 40 ]; 2) the report has to be sufficiently detailed and show the results per each gene and variant tested, therefore the level of evidence of each of them according to guidelines can be considered when choosing the antidepressant.…”

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“…In 2020 thirteen panels of tests are available in Canada to assess patients' pharmacogenomics relevant to medications for depression and 17% were associated with an actionable drug label or guideline for the patients tested. If family physicians could access such tests, obtain medication blood levels, use the guidelines, and consult with a pharmacist specialised in pharmacogenomics they could optimise their prescribing [82].…”

“…The costs ranged from CA$199 to CA$2310 with a median of CA$499. For five tests the results could be reported directly to patients [82].…”