Perils in online genetic tests

Australian experts warn that genetic tests sold directly to the consumer could be a waste of money, because not enough is known about the genetic basis of most diseases.

The tests tell people little more than could be gleaned from a family medical history. And with no genetic counselling at hand, people can be at the mercy of their own anxieties and imagination.

"Right now, the quality of the tests is variable and the results are hard to interpret," says Anne Turner, the head of genetics at Sydney Children's Hospital. "A problem is that people expect to learn more than is currently provable."

A profile may report, for example, that a person has a 50 per cent increased risk of developing bowel cancer compared with a person without the disease-associated gene.

But what does that mean? Very little, Turner says: "Nothing that a sensible medical person couldn't tell you anyway." An overweight smoker aged 50-plus, with a strong family history of the cancer, would get much the same prognosis from a doctor, she says.

Three companies offer tests for assessing disease risk: Navigenics and 23andMe in the United States, and Iceland company deCODEme.

Only deCODEme will accept customers from Australia. They scan about a million locations on the DNA code to detect genes associated with 29 diseases (see box).

The way to get tested is simple: sign up and pay online between $1070 to $2725, and a kit to collect inner-cheek scrapings is posted to your door. You return the specimen, and results are available in about a month. The test data are stored online in a privately accessible account and the results are used to build up databases.

What is not so simple is what to do with the information once you have it.

DeCODEme's website includes a comprehensive disclaimer saying that their results do not represent anything like medical or diagnostic information, but are "designed to get you acquainted with your genetic code."

The criteria that deCODEme uses for inclusion of a disease for testing is that the association between the disease and a gene has been found in a minimum of two studies. "I'm not saying there isn't some scientific underpinning to the tests," Dr Turner says. "But using a small number of research papers and extrapolating these for every individual patient is a problem."

John Christodoulou, the head of the Western Sydney Genetics Program at Westmead Children's Hospital, says common disorders listed by deCODEme are caused by many genetic variations, and a complex interaction between genes and the environment.

"Multiple genes can be associated with an increased risk of a disorder, each exerting a small effect - plus there are environmental factors like exposure to toxins, alcohol consumption, the foods we eat," Professor Christodoulou says.

"Translating these results to an individual is premature."

The tests do not take into account all the possible variations in DNA, nor those that remain undiscovered.

In Australia, genetic testing for medical conditions is strictly controlled. A doctor's referral is required, with the testing carried out at an approved laboratory. Pre- and post-test counselling is also a vital part of the process - a feature lacking in direct-to-consumer testing.

A free public meeting, Direct-to-consumer DNA testing: marketing hype or medical breakthrough?, will be held tonight from 6-8 at the State Library of NSW with speakers including the president of the Australian Law Reform Commission, Professor David Weisbrot, and geneticist Professor Ron Trent. Bookings: Jodie Keen 62179121.

OVER-THE-COUNTER TESTING

* Shampoo, wrinkle-free cosmetics and a diet and exercise program tailored to your DNA are among more than 40 genetic tests spruiked directly to consumers by more than 35 private laboratories worldwide.

* In Australia, testing is limited mainly to establishing paternity or ancestry, plus a new single-gene test for athleticism. Costs $100 to a few hundred dollars.

* For A$350,000 (NZ$443,000), you can buy a copy of your whole genome - all the 3 billion "letters" in your DNA code - from US company Knome, which is in partnership with China's Beijing Genomics Institute.

* Overseas companies offer genetic testing for predisposition to 17 to 29 medical conditions. Costs from A$1075 to A$2725.

* Diseases tested for include: abdominal aortic aneurism, age-related macular degeneration, Alzheimer's disease, asthma, atrial fibrillation, breast cancer, coeliac disease, colorectal cancer, Crohn's disease, exfoliation glaucoma, heart attack, hemochromatosis, intracranial aneurism, lactose intolerance, lung cancer, multiple sclerosis, obesity, peripheral arterial disease, prostate cancer, psoriasis, restless legs syndrome, rheumatoid arthritis, type 1 diabetes, type 2 diabetes, venous thromboembolism.

- © Fairfax NZ News