The context of genetic testing matters – here’s why


medical and predictive genetic testingThere are many different contexts in which genetic testing is undertaken. This has profound impact on delivering genetic medicine well, particularly in relation to test availability and data interpretation. Unfortunately, these contextual implications are seldom considered. One-size-fits-all policies are typically adopted.

Perhaps the most simple and most important context requiring consideration is whether the test is being performed in a patient with a medical condition (medical genetic testing) or in a healthy individual (predictive genetic testing). Most testing services have the same access and consent processes for the ill and for the well. This is inefficient, inappropriate, inconsistent and is restricting the potential for genetic medicine to help the sick.

 

Medical genetic testing

Genetic testing in an ill patient is called ‘medical genetic testing’ and is equivalent to any other medical test

If a genetic test is performed in a patient with a medical condition it is called ‘medical genetic testing’ or ‘diagnostic genetic testing’. Such tests can, and should, be considered equivalent to other medical tests, such as MRI scans. They are part of the panoply of information that doctors obtain so they can give the correct diagnosis and the correct treatments.

There are no major ethical considerations about such tests and decision-making for most people is straight-forward. If a patient is asked – ‘This genetic test will help us to diagnose and treat your illness better, would you like it?’ – the overwhelming majority of people will say ‘yes’. Societies the world over unconditionally believe in the concept of trying to make the ill better.

 

Predictive genetic testing

If a genetic test is performed in a well individual, to try to provide information about future risk of disease, it is called ‘predictive genetic testing’. Such tests are very different from standard medical tests and there are no social norms to aid decision-making. At the societal and individual level there is currently no consensus about how to deal with ‘window-into-the-future’ information.

The possibility of predictive genetic testing therefore throws people into unfamiliar territory, conceptually and practically: Do I want the test? When do I want test? How likely is the test to be positive? If positive, how likely is it that I will get the disease? Will I know when, or how I will be affected? Can I do anything about it?

 

When is genetic counselling needed?

People should feel fully informed when they agree to any test, in any context.

For predictive genetic testing, detailed discussions addressing the above questions with an expert guide in this type of decision-making is almost always helpful and appropriate. This is called genetic counselling.

However, separate, protracted, specialist genetic counselling is not necessarily needed every time a genetic test is undertaken. In medical genetic testing the standard communication and consent processes are often more appropriate.

Indeed, many genetic diagnoses are made through clinical examination by a non-geneticist, without prior genetic counselling. The genetic test is done as a confirmation and referral to genetics to discuss the wider implications for the patient and family occurs after the diagnosis has been made. This is how medicine works, and what society expects; first treat the patient then consider other issues. Yet, when a genetic diagnosis can only be made through a genetic test, for example in BRCA-related cancers, genetic counselling is often said to be mandatory, whatever the context of testing.

As well as being inconsistent, this leads to limited testing availability for patients, because access to genetic counselling is a major bottleneck for most healthcare systems. Many cancer patients wanting a BRCA test to know if PARP inhibitors are a treatment option for them are unable to get a timely test because waiting lists for genetic counselling are so long. This is very regrettable and avoidable.

To address this for BRCA testing we have implemented access to testing within cancer clinics, consented by the cancer team. This is sometimes called ‘mainstream genetic testing’. Patients with a BRCA mutation automatically get a genetics appointment to discuss wider implications, but this consultation happens when the result is known.

Nearly 1000 patients have been offered a mainstream BRCA test in our institution. Only one did not want it. This further shows that decision-making for medical genetic tests is straight-forward, for most people. Mainstream testing has proved very popular with patients and the medical teams.

 

Medical genetic testing should become part of routine healthcare

We should aspire for most medical genetic testing to be integrated into routine healthcare, with expert genetics input deployed only where needed

We should aspire for most medical genetic testing to be integrated into routine healthcare, with expert genetics input deployed only where needed, for example, patients in which the test reveals a mutation.

The mainstream testing model for medical genetic testing is not only easier for patients, it is more time and cost-effective. Most importantly it will enable genetic medicine to benefit many more patients.