DNA testing is big business. When it comes to wellbeing, information is everything and this couldn’t be truer for the cells in your body. Those microscopic units of living matter shedding off inside your cheeks and in your saliva carry huge secrets to your entire genetic code – everything from which skincare will best suit you to details about your ancestry and your predisposition to life-threatening diseases. And if a harmful change in someone’s genetic makeup is discovered, then a targeted treatment plan for each individual can also be gleaned.

Given the power that lies within the genes – literally life and death in some cases – millions of people worldwide are opting to spit in a test tube to unravel every detail about their A, C, T and G strings. Getting the lowdown on your deoxyribonucleic acid is a fast-growing health trend.

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What is Genetic Testing?

Easy, rapid and relatively affordable, genetic tests look for mutations in DNA and give a predictive score of disease risk by aggregating the contributions of the tiny chemical strands in thousands of genes. They can gauge susceptibility to a wide range of conditions such as asthma, type 2 diabetes, coronary artery disease and cancers of the breast, ovary and prostate.

Tests for specific sicknesses like breast and ovarian cancer linked to mutations in the BRCA-1 and BRCA-2 genes have been available in clinical settings for decades and are valuable tools in disease prevention. Yet, the recent avalanche of unregulated home DNA kits and a new generation of state-of-the-art private labs offering ‘direct-to-consumer’ predictive genetic testing are more problematic. They have been criticised for giving incomplete, uncontextualised information so people may end up with more anxiety than clarity.

DNA sequencing does not provide a clear-cut finding like a pregnancy test; it’s more akin to a weather report. For example, it might predict your lifetime risk of prostate cancer at 15-percent, which is marginally higher than the average risk of 12-percent. Is this score sufficiently concerning to prompt drastic action, or should the result be viewed with scepticism? Many people who sign up for a direct-to-consumer genome evaluation expect a precise ‘yes’ or ‘no’ on serious diseases and are ill-prepared for the ambiguity it may reveal.

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Problem of Probability

The results of gene analysis may seem definitive – if there’s a gene mutation it increases the risk of disease; if there isn’t the risk is negated – but it is rarely that simple. It’s a matter of degrees, and the outcome of taking a predictive test can be profound. For example, since a mutation in the two BRCA genes signifies a 60-percent to 90-percent risk of breast cancer, a woman in receipt of this finding might opt for a preventive double mastectomy – remember the ‘Angelina Jolie effect’ – yet they may not have the full picture.
When you go to a doctor for a heart attack, stroke or cancer examination, the physician reviews your complete family history, takes your ethnicity into regard, scans for many unusual alterations of the gene, and then interprets your overall disease risk. Direct-to-consumer tests, on the other hand, only screen for a few of the common mutations of the gene and flash up your risk probability ratio. It’s an incomplete answer, and it might be a false negative.

Another issue is that while DNA stays the same, the research linking mutations to genes is in a constant state of flux, so much so that scientists find new information on a regular basis. There are still a lot of unknowns in the association of certain genetic variations with specific diseases. What’s seen as benign or harmless today might be considered dangerous tomorrow. And vice versa.
Case in point – a study by US molecular diagnostic company Myriad Genetics of 1.45 million patients who took hereditary cancer genetic tests from 2006 to 2016 found that the disease risk result of 60,000 people was reclassified over time. Many were downgraded to benign or likely benign, while some were upgraded to pathogenic or likely pathogenic – a rude shock for those who had assumed from an earlier test that they were going to live a fairly healthy life.

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Dawn of Genome Medicine

Advocates of predictive genetic tests say that any information about your DNA is better than none at all. The argument is that since there is no potential health risk to spitting your saliva in order to uncover a plethora of usually accurate (though incomplete) information, then go ahead. The outcome may be weak now, but it proffers a greater good: the possibility of personalised medicine.

Precision medicine – looking at a person’s genes, environment and lifestyle in order to determine a personalised program of treatment that gives them the best chance of recovery – has been a hot topic for more than two decades. Gene scientists insist that with a genome map cancer can be treated with one’s own immune cells in the not-too-distant future. While curing cancer is certainly the icing on the cake, widespread DNA testing should be beneficial in all aspects of care. For starters, the vague markers used today – like a patient’s height and weight – could be replaced with much more detailed and targeted information. The end result would be more specific diagnoses and better medication choices with fewer side effects.

As vast datasets are accumulated by private genetic analysis labs and (regulated) DNA biobanks created for genetic research, the pace of medical innovation is mind boggling. Understanding how genes and environmental factors variously impact disease is a huge step towards making personalised medication a reality in the future.

(Text: Nikita Mishra)