Genomics in general practice


Personal genomic testing: More information
☰ Table of contents


What is personal genomics?


With the advancement of gene sequencing technology, genetic testing is increasingly moving beyond the clinic and tertiary medical centres, and into the community. This new form of testing is readily accessible via the internet, either through a health practitioner or by patients themselves, and represents the new world of personal genomic testing (PGT).1

Clinical genetic testing has traditionally been used to gather information or confirm a diagnosis of a condition in an individual showing symptoms. Testing has also been used to screen asymptomatic populations, such as carrier screening for recessive conditions. Until recently, these genetic tests have been targeted, looking for particular gene variants (or mutations) in specific genes. Clinical support, including genetic counselling, has generally been available to help individuals interpret and manage genetic test results.

However, new technology (eg Single nucleotide polymorphism [SNP] genotyping) can now examine thousands of gene variants throughout a person’s genome. New sequencing technology also allows the entire sequencing of an individual genome (whole genome sequencing) at a relatively low cost. The availability of such technology is challenging the traditional model of genetic testing.2,3

Asymptomatic individuals now have the opportunity to access ‘direct-to-consumer’ (DTC) or ‘at-home’ testing through a range of private providers.
Some DTC companies require a health practitioner to order a test on behalf of the consumer and take delivery of the test results, while others do not. A test kit provided by the DTC company is used to collect a cheek swab or saliva sample and mailed back for analysis. In some cases, results are returned to the consumer without comprehensive interpretation and/or clinical support.

 

What is tested?


PGT can provide information that is health or non-health related.4 Non-health related information includes:

  • physical traits (eg red hair, freckles)
  • genetic relationship testing (eg paternity testing)
  • ancestry.

Some tests offer information that have health-related implications to varying degrees. In some cases, the tests are the same as those offered in regular clinical settings. Personal genomic tests might include genetic variants that:

Some companies test for variants for other health-related information that are more uncertain, such as variants with low penetrance, or with limited evidence to support associations with disease.3 These tests might include genetic variants that are:

  • much more weakly associated with susceptibility to disease (eg complex conditions such as type 2 diabetes, rheumatoid arthritis)
  • marketed to predict sporting ability, including fitness and response to training regimens
  • professed to provide information about response to diet and nutrition (nutritional genomics) or weight loss (eg MTHFR gene testing). In Australia, these tests are advertised as ‘genomic wellness’ tests, and are increasingly available through naturopaths and nutritionists.  
 

How are results reported?


Companies may report estimates of risk from test results in a variety of ways, including odds ratios, percentages, comparisons with average population risk (using a reference population) or lifetime risk. It is important to note that not all companies use the same reference population and consumers may be a different ethnicity to the reference population.

Companies may also vary in the way they produce their estimate of risk (eg use of different algorithms). Consequently, test results from one company may not match those from another company, even with the same deoxyribonucleic acid (DNA) sample.

Customers are often able to download their ‘raw data’ (ie the actual variant or SNP data), which may provide health-related information beyond what the original test results provide. This extra information often comes with no interpretation provided to the consumer. Consumers can also upload their raw data to online databases (or to genetic testing companies) where a further level of analysis is available. Again, this is often provided without appropriate clinical support.

 

Considerations with PGT


Questionable credibility

PGT companies use a combination of marketing rhetoric, and unsupported claims and research evidence to promote their product. In many cases, there is no clinical support. The ability of these tests to accurately predict outcomes (clinical validity) is variable. Consumers are faced with a difficult task of determining the credibility of these tests.

 

Regulatory landscape

The technology around PGT is changing rapidly, as is the variety of testing. Given the international reach of PGT, regulation of the industry is challenging.

 

Empowered patients

There are many who support PGT as a means of empowering consumers to proactively manage their health (ie clinical and personal utility). Others suggest individuals may be misled by information with poor clinical validity, leading to unnecessary costs that are a burden to the consumer and health system.

 

Privacy and confidentiality

Information obtained by an individual can have implications for other family members, especially those who may not want to know. Given the ease of testing, some people (eg children) may be tested without full consent.

The ownership of the data from testing is another complex issue. If a testing company changes ownership, so does the data. Some consumers choose to share their genetic information or data (eg online) which can also allow for unintentional access by others.
 

Personal utility

For many individuals, the concept of personal utility seems more relevant than the clinical utility of testing. Personal utility includes the value of increased knowledge about oneself (where curiosity often motivates individuals wanting to be tested), increased knowledge about the trait or condition tested, potential for anticipated coping, and altruism (eg helping research as a motivation for testing, with opportunities for data sharing through not-for-profit websites or organisations).5,6


 
 

Implications for general practice


The uptake of PGT is likely to continue, and general practitioners (GPs) will increasingly encounter patients who are curious about or have used PGT.
Some PGT companies recommend using specific practitioners (ie those they nominate who may have undertaken some training) who will order the test on behalf of the consumer. Some of these companies may also provide genetic counsellors who can discuss the results with the consumer.

Other companies state that the PGT reports are provided for information or educational purposes only. They may state that the consumer should talk to their GP or other health practitioners about their results. However, practitioners themselves may have a limited understanding of the nature of the test or its interpretation.

Involving health practitioners in the process, either in ordering tests and/or interpreting results, may have positive and negative consequences. Some health practitioners, including GPs, may not feel confident in supporting patients to understand their results.1,5

There is also the potential to overburden the healthcare system with subsequent inappropriate ordering of health services, including referral to genetics services when it might not be warranted. Some genetic services no longer accept referral for most people who have had the MTHFR gene testing, as its clinical validity and utility is questionable.

The National Health and Medical Research Council (NHMRC) has developed a PGT resource entitled ‘Understanding direct- to-consumer (DTC) genetic DNA testing: An information resource for consumers’. GPs can use this document to discuss PGT with patients who are interested in ordering a test.

Potential consumers of PGT testing should consider all aspects when they are thinking about having one of these tests and GPs can play an important role in raising these issues with their patients.7


Genomics in general practice




 

 

  1. Brett GR, Metcalfe SA, Amor DJ, Halliday JL. An exploration of genetic health professionals’ experience with direct-to- consumer genetic testing in their clinical practice. Eur J Hum Genet 2012;20:825–30.
  2. Kalf RRJ, Mihaescu R, Kundu S, de Knijff P, Green RC, Janssens CJW. Variations in predicted risks in personal genomic testing for common complex diseases. Genet Med 2014;16:85–91.
  3. Bunnik EM, Schermer MH, Janssens AC. Personal genome testing: Test characteristics to clarify the discourse on ethical, legal and societal issues. BMC Med Ethics 2011;12(1):11.
  4. Felzmann H. ‘Just a bit of fun’: How recreational is direct-to-customer genetic testing? New Bioeth 2015;21(1):20–32.
  5. Covolo L, Rubinelli S, Ceretti E, Gelatti U. Internet-based direct-to-consumer genetic testing: A systematic review. J Med Internet Res 2015;17:e279.
  6. Bunnik EM, Janssens AC, Schermer MH. Personal utility in genomic testing: Is there such a thing? J Med Ethics 2015;41(4):322–26.
  7. ACMG Board of Directors. Direct-to-consumer genetic testing: A revised position statement of the American College of Medical Genetics and Genomics. Genet Med 2016;18(2):207.

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