Page last updated at 16:45 GMT, Thursday, 9 April 2009 17:45 UK

How spit test can screen your genes


Linda Avery, co-founder of the genetic screeing company 23andMe, talks about the process

Would you like know what your genes say about your health - and have a prediction as to what diseases you might be vulnerable to?

Then be prepared to spit and cough up some cash.

There has been a big increase in the number of online companies offering genetic tests.

BBC medical correspondent Fergus Walsh went to 23andMe, based in California, which claims it is democratising access to genetics.

The starting point with 23andMe, as with many genetic tests these days, is the internet.

Their kit costs $399 which you order online. Inside is a test tube into which you give a spit sample and then post it off to a laboratory in California.

Scraps of DNA found in cheek cells floating in the sample are analysed.

They look for things called SNPs or single nucleotide polymorphisms (pronounced snips). These are minute variations in your genetic code, some of which may put you at less or greater risk of disease.

The offices of 23andMe in California's "silicon valley", are just south of San Francisco and just a stone's throw from the headquarters of Google.

That is perhaps not surprising because the two companies are linked, by marriage and money.

Anne Wojcicki, who helped set up 23andMe is married to Sergei Brin, one of the Google co-founders. Google has also invested in the company.


Ms Wojcicki's business partner, Linda Avey, says: "We want to be the trusted source of your genetics."

Their website gives information about scores of conditions and traits for which there are genetic associations including age-related macular degeneration (the most common cause of blindness in the elderly), diabetes, Parkinson's, and rheumatoid arthritis.

"There are now over 90 conditions that we examine", says Ms Avey.

"They range from the type of earwax you have, to cancers that you might have higher or lower risk for.

"We take that research and we distil it down into those different topics and then explain it to you based on your own genome and what is understood at this point".

Most chronic diseases have both genetic and environmental causes - your genes play a part, but so does your lifestyle.

Marcy Darnovsky
Marcy Darnovsky, from the Center for the Genetics and Society in California, is worried about direct to consumer tests

Up to 70% of cases of macular degeneration may be genetic in origin, compared to only 25% of type 2 diabetes.

Where genes are a factor there are usually lots of them involved.

Scientists only understand a tiny proportion of the genetic variations found in our DNA. So interpreting what your genetic profile results mean for your health is not straightforward.

A couple of weeks later I received an email telling me my results were ready.

Feeling both curious and apprehensive I logged onto my account. I wanted to know what cards my genes had dealt me.

For the most part it was pretty good. Apart from a slight increased risk of psoriasis (a skin condition), the results seemed pretty good.

All except for one risk factor - venous thromboembolism - blood clots. These can be fatal.

The average lifetime risk is 25% - so for every 100 people, 25 will have a blood clot at some point in their life.

But my risk was 61%. Put another way, for every 100 people sharing my genotype 61 would get a venous thrombosis.


That seemed a bit alarming. There is quite a bit of explanation on the website, with comments from other members of the 23andMe "community" (people who've had the test).

But unlike traditional hospital-based genetic testing, there is no counsellor on hand to talk you through the results.

This is a potential flaw of most direct to consumer genetic tests. There is no face to face counselling involved, either before or after your test.

There is plenty of helpful advice to read, but no-one to talk to about your results. You get them online and have to cope with whatever they throw at you.

Marcy Darnovsky, from the Center for the Genetics and Society in California, is worried about direct to consumer tests.

"There are basic questions about their accuracy and there are serious questions about what these results might mean and whether they might present some potential for harm to individuals."

My results came through after I'd returned to the UK so I decided to show them to a genetic counsellor.

Christine Patch works at Guy's and St Thomas' Hospital in London.

She said 23andMe's website was slick and well presented, but "If you wanted to find out about your own health I would say it's a waste of money.

Spit kit
The kit costs $399 which you order online

The thing about common diseases such as type two diabetes and cardiovascular disease is they are complex and just measuring one or two variations may not give you the whole picture."

As to my apparent heightened risk of blood clots, she was also reassuring: "You have to remember that the risk of getting blood clots is quite high, and about half the risk is down to environmental factors, and other genetic factors, so the chances are you will live your life without getting one."

23andMe certainly do not claim to have all the answers and regard the genetic results they offer as a work in progress.

The site is regularly updated to reflect new research findings on genetic links to illness, so your personal risk profile keeps changing.

Of course we all know how to reduce our risk factors for disease - have a healthy diet, regular exercise, don't smoke and don't drink to excess.

Christine Patch says if you want to know about your health then getting your blood pressure checked or measuring your body mass index would give you more useful information.

Nonetheless, having your DNA screened does give you a fascinating insight into genetics and the chance to join and compare DNA details with a growing online community of gene-tested individuals.

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