Genetic testing: Sometimes you might die

4. March 2011

A visit to the family reunion reveals more about one's own medical future than any genetic test, since risk genes alone are by no means the cause of disease. Tests open to everybody are a nice gimmick anyway.

What happened to all the hopes, that diseases will soon be able to be predicted? When Bill Clinton and Tony Blair appeared before the press ten years ago and announced the complete map of the “Book of Life”, excitement and anticipation were high. With the sequencing of our genome, it would soon be possible to predict from what one will probably die. Progress in the field of genetic diagnostics has indeed been enormous – at any rate, in the reduction of costs. While the first project did consume millions, a mini-sequencing for anybody can be ordered today for a few hundred euros from companies such as “23andMe” on the Internet.

Old-fashioned family medical history?

Yet family medical histories seem almost antiquated. Why ask Uncle Bernie what his mother died from, when one can just do a genetic test to find out which genes one has collectively? There still is, however, between what is technically feasible, and the uses of knowledge for the individual, a gaping big hole. The conclusions that can be drawn from the row of letters are not particularly grand. Studies that can show a link with certainty between a gene and a disease are few and are for the most part wrong. The most recent example is probably the gene KIF6, which was suspected to increase the risk of cardiovascular disease by 20 to 50 percent. It was not long before there existed the appropriate genetic test for a hundred dollars. One may as well pull out the Tarot cards. A study in the Journal of the American College of Cardiology of 57 000 subjects last year showed that KIF6 has no effect on the risk of disease.

Other gene variants do play a measurable role, when placed in relation to other risk factors such as age, gender or lifestyle however, we suddenly find that they are in most cases barely of any consequence. This does not mean that genes and knowledge about them would be unimportant. They merely have to be seen in the right context, such as the influence of the family. For one doesn’t only share risk-genes with one’s relatives, but many other genes as well. And all interact with each other. One gets a glimpse of their influence when one looks to the study of Charis Eng, the director of the Genomic Medicine Institute (GMI) of the Cleveland Clinic. She found a big difference between the prognosis of cancer risk by DNA test and of that via family history and presented the results at the annual meeting of the American Society of Human Genetics (Asgher). The strike rate for breast, colon and prostate tumours were, with the family data analysis, clearly higher. The family history diagnoses revealed, for example, eight people correctly with a high risk for breast cancer. With the DNA test there was only one. Many of the commercial DNA tests only look for one or two major mutations, other alterations that also increase the risk for breast cancer are often not pursued. Also none of the patients with hereditary colorectal cancer was classified by genetic analysis as high-risk patient. “Family history diagnosis of cancer has a greater predictive power than DNA testing,” is the clear conclusion according to Eng. A clear correlation between gene x and disease y occurs only rarely. Cystic fibrosis (mucus of the respiratory tract) or Huntington’s disease would be such examples. Most of the common human diseases, however, arise from a mix of different genes and environmental factors. And so the ASHG now also defines family history analysis as the “golden standard”.

Unfiltered access to medical prognoses

One concern with DNA analysis could now perhaps be eliminated. Scientists and doctors were very concerned that people who, by way of unfiltered access to their medical prognoses, could be distraught, frightened or even could be traumatized by the result. A new study, released in the U.S. journal “New England Journal of Medicine“, shows a sobering picture.

For the study, the genomes scans of more than 2000 subjects were examined. In so doing, the risk for more than 20 diseases such as obesity, diabetes, rheumatism, various types of cancer, multiple sclerosis and Alzheimer’s disease was determined. Almost six months after the volunteers had the 90-page report on their future health in black and white before them, they were examined for signs of anxiety, for striking changes in their eating habits and on their fitness activities.

“We observed in 90.3 percent of subjects no signs of harmful stress or any increase in follow-up investigations.” The subjects also, now knowing their risk, did not start being physically more active or take in less fat. There was also no trace of anxiety. However, 26.5 percent discussed the results with their doctor. In addition, almost half of the subjects ended the study prematurely; these were perhaps the people who feared the test evaluation. After the evaluation, the patients with a known degree of risk for a few of the studied diseases expressed that they would have themselves tested more frequently in future. The authors estimate this risk, however, as a low one. This is a good thing, as most screening programs are pointless for people who show no symptoms.

It seems that many people want to simply possess this information about their genes, without being alarmed by the results. They want to possess the information even though they have to pay for it and accept the, as is known, only very limited health-relevant conclusions.

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