Direct-to-Consumer Genetic Testing

Developed by Dr. June Carroll, Ms. Shawna Morrison and Dr. Judith Allanson

Last updated April 2014

Disclaimer

• This presentation is for educational purposes only and should not be used as a substitute for clinical judgement. GEC-KO aims to aid the practicing clinician by providing informed opinions regarding genetic services that have been developed in a rigorous and evidence-based manner. Physicians must use their own clinical judgement in addition to published articles and the information presented herein. GEC-KO assumes no responsibility or liability resulting from the use of information contained herein.

Objectives• Following this session the learner will be able to:– Discuss and address patient concerns regarding direct-to-

consumer genetic testing– Find high quality genomics educational resources

appropriate for primary care

Case

• Jim, 53yo male • Healthy, active, non-smoker• Has been your patient for 15 years• Recently promoted as a corporate executive

and is being asked to undergo a thorough medical evaluation including personal genome testing and would like to know your thoughts

Family history

26

JimA&W

3A&W

JudyA&W

A&W

5453

42

A&W

A&W A&W

N

Prostate cancer

d.79 82

HypertensionArthritis

54Mid-50s

A&W

What is direct-to-consumer genetic testing?

• Direct-to-consumer (DTC) genetic testing also referred to as personal genome testing– offered with the promise of providing:• predictive genetic risk assessment for a variety of

health conditions (i.e. diabetes, cancer, obesity) • information about carrier status• information regarding response to and/or side-effect

risk of certain pharmaceuticals (i.e. clopidogrel, statins, antidepressants)

• Uses odds ratios and relative risks to categorize an individual as at increased risk (higher than average), average, or at decreased risk (lower than average)

• Can also screen for single gene disorders (e.g. cystic fibrosis, HFE-associated hemochromatosis, BRCA)

• Can uncover medically irrelevant information such as bitter taste perception or curly hair

What is direct-to-consumer genetic testing?

What do I need to know about the genetics of direct-to-consumer genetic testing?

• Uses data generated from genome-wide association studies (GWAS) – case-control studies which examine many common

variations in our genetic code (single nucleotide polymorphisms [SNPs])*

– compare large groups of individuals (unaffected controls versus individuals with symptoms of a specific disease) in an attempt to distinguish between non-harmful changes in the DNA code and pathogenic, disease-causing/predisposing changes

SNPs (pronounced ‘snips’) are the most common type of genetic variation. Each SNP represents a difference in a single DNA building block, a nucleotide. SNPs occur normally in an individual’s genome about once in every 300 nucleotides, and so there are about 10 million SNPs in the human genome

Who can obtain direct-to-consumer genetic testing?

• Generally, direct-to-consumer (DTC) genetic testing is available online to anyone for a cost

• Genetic testing for DTC genetic testing is usually performed on a saliva sample

How will genetic testing help you and your patient?

• While there are limited data to support the clinical validity (ability to predict clinical outcome) and utility (the likelihood of improving patient outcome), some consumers might benefit from direct-to-consumer genetic testing as results may:– Encourage positive behaviour modifications (e.g. increase

exercise, smoking cessation) – Provide useful information for medication choice and/or dose,

or management – Provide information to individuals who have no or limited

information about their family history (e.g. an individual who was adopted)

– Reveal carrier status of a genetic condition that could have implications for family planning or medical management

Are there harms/limitations of direct-to-consumer genetic testing?

• Caution when interpreting direct-to-consumer (DTC) genetic testing should be exercised as:– DTC genetic testing does not take into account numerous

factors important when interpreting genetic test results such as age, family history, lifestyle (e.g. smoking, obesity) and other environmental factors that are a significant contribution to common complex disease development

– Questionable clinical utility of some of reported results– Family health history-based risk assessment is still the

gold standard in the initial assessment for heritable conditions

• No testing regulation• Concerns re downstream testing and costs as result

of direct-to-consumer (DTC) results• “misattributed equivalence” – if a DTC test indicates a lower than average lifetime risk for

a certain condition, when FH indicated a much higher risk, a consumer could be falsely reassured and not be as vigilant about medical interventions indicated by FH

– This phenomenon speaks to the need for knowledgeable healthcare provider involvement in pre- and post-test counselling

Are there harms/limitations of direct-to-consumer genetic testing?

• Pearls– Direct-to-consumer (DTC) genetic testing is over-the-counter

genetic testing available online to consumers through private companies

– Generally, results report an individual’s probabilistic risk to develop a medical condition based on genome wide association studies (GWAS)

– Results may provide medically useful information for consumers in addition to medically irrelevant information (e.g. curly hair)

– Interpret DTC results with caution– Family health history-based risk assessment is still the gold

standard in initial assessment for heritable conditions

References• Aiyar et al. Risk estimates for complex disorders: comparing personal

genome testing and family history. Genet Med 2013;. [Epub ahead of print]

• Goldsmith L et al. Direct-to-consumer genomic testing: systematic review of the literature on user perspectives. Eur J Hum Genet 2012; 20:811-816

• Heald B et al. Prospective comparison of family medical history with personal genome screening for risk assessment of common cancers. Eur J Hum Genet 2012; 20(5):547-51

• Special thanks to genetic counsellor Jill Davies at The Medcan Clinic