Medical testing to diagnose the cause of disease is part of everyday clinical practice. It includes taking measurements of height and weight, analysing blood samples for a range of different chemicals, using high-tech imaging machines to investigate lumps and bumps, and so on. Genetic testing – which usually means sequencing DNA to determine the cause of a specific condition in an individual – is just one of a rich variety of tests that clinicians employ to do their jobs.
Nonetheless, genetic testing is frequently considered separately from other types of tests, and genetic information is often treated somewhat differently than other information – a practice known as ‘genetic exceptionalism’. Unlike most biological molecules, DNA has its own medical specialists, counsellors and laboratory scientists, as well as large national projects (see Genomics England, for example). In addition, legislation exists to prevent discrimination specifically based on genetic information (see the Genetic Information Non-discrimination Act in the USA, and the Association of British Insurers’ Concordat and Moratorium in the UK).
Does medical genetic information merit special consideration?
The use of the term ‘exceptionalism’ in a medical context did not originate with genetics, but with infectious diseases. The term was first introduced into the literature in 1991, when the term “HIV exceptionalism” was coined to describe and critique the policy of treating the human immunodeficiency virus (HIV) differently from other infectious diseases. Although HIV exceptionalism has been long abandoned, the idea that genetic information requires special treatment has persisted, and numerous arguments have been put forward in favour of genetic exceptionalism, including:
- the long-term stability of DNA
- the immutability of genetic information
- the broad applicability of genomic information
- the uniquely identifying nature of some genetic information
- the enormous predictive power of some genetic tests
- the role of genetics in personal identity
- the familial and ancestral nature of genetics
- the potential for stigmatisation
However, none of these properties are unique to DNA. Genetic information is not distinctive in its potential to predict future health, nor its importance for families, nor its potential for stigmatisation. In fact, genetic data are not wholly different from other data collected for medical purposes.
In its 2002 report Inside Information, the UK Human Genetics Commission concluded that although none of the properties of DNA alone are unique and many are also true for other types of health-related information, nonetheless “their cumulative effect was such as to justify the according of special status to this type of information”. The Commission also emphasised that “it is often inappropriate to treat all personal genetic information as a special class of medical information. The notion that genetic information is always sensitive rests on the common misunderstanding of the predictiveness of most genetic information and the importance of one’s genes in developing disease”.
Moving from genetic exceptionalism to genetic realism
One of the reasons for the different treatment of genetic information is an erroneous belief in genetic determinism. In fact, as this blog has explored previously, human genomes have an enormous amount of variation and, far from being deterministic, the effect of this variation on human health and disease is enormously complex, probabilistic and hard to interpret. Most genetic variation is benign, and unconnected with human traits or diseases.
Unfortunately, the exceptional treatment of genetic information can result in overzealous data protection initiatives, overhyped expectations, and ultimately unsafe medicine. We must apply the same rigorous principles to genetic tests as we would for any other clinical tests, but no more. Just like any other clinical test, genetic testing can be incredibly powerful for some people, but there are multiple different ways a genetic test can fail, or produce uninterpretable or irrelevant results, or even give a wrong result. This misinformation can be toxic.
Perhaps the most exceptional thing about genetic information is its volume…
Scientists have only recently started to appreciate the astonishing variability between human genomes. Of the 6 billion letters of DNA in a human genome, we all have over 6 million places where we vary from other people, and many of these are unique to us or our close family members. And yet a change to just one of those letters could hold the key to a diagnosis. Working out which one that might be in an individual is a daunting task! Genetic information is increasingly sifted and sorted by computer algorithms, which require substantial expertise to design and run, as well as significant memory to store and analyse DNA sequence data. These algorithms – like laboratory tests – are imperfect and can produce both false positive and false negative results.
So rather than genetic exceptionalism, we need to make sure we take a proportionate and realistic approach to genetic information that appropriately balances the potential benefits with the potential harms. Only by developing best practice and sharing knowledge and data can we be sure to practice the safest and most effective genetic medicine.