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How Accurate Are Those Home DNA Tests?

Can a cheap, off-the-shelf paternity test really be accurate?

By Dave SmithPublished 5 years ago 3 min read

Analysing a person's DNA was once a difficult, time-consuming, and expensive task—reserved for the police, and performed in high-tech laboratories. But these days, you can pick up a home paternity test from a discount store for as little as £5 (plus a lab fee of around £100 for processing the samples). But can you really trust a cheap, at-home DNA test?

The short answer is yes. But please read on to find out more...

It depends who does the test

Just do a quick Google search for "DNA testing" and you'll be flooded with links and ads for DNA testing companies—some of which may offer very enticing prices. But to make sure you get an accurate result, you really need to choose an accredited testing lab.

In the UK, UKAS is a widely-used and trusted accreditation body. Look out for their logo and the ISO 9001 quality management mark, along with the ISO 17025 mark (which applies specifically to testing and calibration laboratories).

In the United States, take a look at the DNA Testing Choices website—they're an independent and impartial organisation that collects reviews and feedback on different testing labs.

It also depends on which type of test you order

There are two main types of DNA test—Peace of Mind and Legal.

A Peace of Mind (POM) test is purely for your own information, and cannot be used in court or to settle legal matters. Why?—because you provide the DNA samples yourself, with no witnesses or proof that the samples haven't been tampered with. The home paternity tests that you can pick up in a pharmacy are classed as Peace of Mind tests.

A POM test is accurate—just as long as the correct samples are provided.

A legal test can be used in legal matters. For a legal test to be valid, the DNA samples must be collected by a professional sample collector or a doctor. Your ID will be checked, you may be photographed, and the samples will be transported back to the testing lab under a controlled and recorded chain of custody. Everything is done by the book.

As you might expect, a legal test is usually a little more expensive, but the extra cost is worth it if you need to settle a legal matter—such as a child custody dispute, or an immigration case.

Why are tests only 99.99 percent accurate? Why not 100 percent?

When you order a DNA test, there are two possible outcomes:

  • There is a 0 percent chance that the two people are related, or...
  • There is a 99.99 percent chance that they are related

So why is there a small margin of error? Is the testing science unreliable? Not quite.

It’s because your DNA contains a random selection of genes inherited from both parents, and there is a very small (and we do mean very small) possibility that you and a complete stranger could share the same DNA profile just by sheer chance. The odds of this happening are astoundingly small, but they're not zero. In order to be 100 percent sure, you would have to test a child against every man on the planet!

But don't worry—even with the tiny margin of doubt, a legal test from an accredited lab will still stand up in court.

In summary

Is a cheap home DNA test accurate? Yes—just as long as the testing company is accredited and the samples are taken correctly.

If you need the test for a more official matter, then a Peace of Mind test just isn't gonna cut it—contact a company and arrange a legal test instead.


About the Creator

Dave Smith

Science man.

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    Dave SmithWritten by Dave Smith

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