In February 2001, the preliminary results of one of the biggest research projects ever undertaken were released: the Human Genome project, the complete mapping of the entire genes of a human being. At the time, members of the public, and of the scientific community, thought that this information would revolutionise medicine. Soon, every patient at the doctor’s office would have their own genome sequenced and receive personalised care based on their own DNA. Optimists even thought that if we could crack the DNA code, diseases such as cancer would be a thing of the past.

Fifteen years on and it is still unclear if the promised revolution has taken place. Amazing advances have been made in genetic testing, entirely changing the way we treat certain disorders. But in some ways, we are living in a dystopian future, where for a thousand euro you can send a swab from your cheek across the world and have your personal genome sequenced. The story of how we use genetics in medicine is still complicated and researchers are still discovering new things about DNA. Genome sequencing has revolutionised the field of genetic testing where someone’s genetic sequence can indicate whether or not they have disease-causing mutations.

This is the case for cystic fibrosis, Ireland’s most common inherited genetic disease. Once upon a time, this disease was diagnosed by a midwife by licking a baby’s forehead to see if they had especially salty sweat (a characteristic of cystic fibrosis). Nowadays, the testing is slightly more hygienic. A diagnosis of cystic fibrosis is confirmed by genetic testing, where a child’s DNA is scanned looking for specific disease-causing mutations. Knowing their own particular mutations can be crucial for the patients’ prognosis and treatment.

Genetics has not been the silver bullet against cancer that some might have hoped, but genetic testing has still saved lives in the battle against this pernicious disease. The most famous example of this is testing for BRCA1 and BRCA2 mutations, which are known to cause breast and ovarian cancer. The BRCA1 mutation is perhaps the most famous genetic mutation in the world: it made headlines last year when actress Angelina Jolie revealed she had tested positive for the mutation. Like many women with this mutation, Jolie opted to have a mastectomy and oophorectomy (ovary removal) to prevent developing cancer.

Many people who have a history of cancer in their family can now opt to have a genetic test. If a person is found to have a specific cancer-causing mutation, they can have more regular cancer screening so if cancer develops it is found at an early stage, and if they do develop the disease, treatment can be shaped specific to the genetic profile of the cancer. As a result, genetic testing has measurably improved the prognosis for many cancer sufferers.

Genetic testing is a lot more complicated than was anticipated in 2001. The positive stories, such as cystic fibrosis and BRAC1, are usually diseases caused by one mutation in a single gene.  Researchers in the field have found that diseases are rarely that simple. Most diseases are caused by multiple genes interacting with each other, as well as with the environment. Since the Human Genome Project, an entire new discipline of genetics has flourished: epigenetics, which studies how DNA is expressed and how genes are effectively turned “on” or “off”. For geneticists, it is like coming to the end of a video game and finding out that there is a whole other level, with an even more difficult enemy to face.

“Fifteen years on and it is still unclear if the promised revolution has taken place.”

One positive is that genomic testing has become cheaper and faster in the last fifteen years. It cost upwards of $3 billion dollars and 10 years to get the first genome sequenced; now it is possible to do so in little over 24 hours, at a cost of only $1000 dollars.

An entire cottage industry of companies has sprung up to offer cheap “mini” genomic testing to consumers.  It is now common to see ads on the internet or television for DNA testing. The most well-known company offering these services is 23andMe. For just €169, 23andMe will send you a DNA kit and analyse a saliva sample. They can give you information on a wide variety of genetic characteristics, such as ethnic ancestry and genetic traits. You can also get information on genetic risk factors for certain diseases, such as certain cancers or Alzheimer’s disease, and identify potential poor drug reactions you may have.

One big problem with these miracle tests is that it is still unclear how accurate these predictions are. Even if you have a gene that predisposes you to get Alzheimer’s disease, it doesn’t mean you will definitely get Alzheimer’s disease. The chance may be as low as 20 per cent.

In 2013, the Food and Drug Administration (FDA) ordered 23andMe to stop marketing it’s Personal Genome Service in the United States, citing “the potential health consequences that could result from false positive or false negative assessments for high-risk indications.” For instance, a false positive for a gene that carries an increased risk of breast cancer could lead to a person deciding to undergo unnecessary chemotherapy or even surgery. Similarly, a false negative could lead to someone ignoring an actual health risk. 23andMe stopped including the health related results in the US for two years, until 2015, when it started offering revised FDA-approved results. It still offers health related results in Europe.

Since the Human Genome Project, the science of genetics remains one of the most exciting and growing areas of medicine. Our genetic information is easier to access now more than ever, but our ability to analyse it may take some time to catch up. Until then, consumers may have to take information they learn from a cheek swab with a pinch of salt.