What is a home DNA test kit?

Written by Ellen Hinkley
24 January 2019

These days, most people are familiar with the idea that DNA contains the blueprint of our existence. But it is only relatively recently that DNA testing has become available to the public. Most people have been aware for a while that DNA testing can used for confirming paternity, or identify suspects in criminal investigations.

Home DNA tests are opening up science to us all, from the comfort of our own homes. With the rise of private genetic testing, customers are able to make use of their genetic information to gain a wide range of insights into themselves. Home DNA kits used to be offered by only a few niche companies, but are now being sold by a wide selection of providers from around the world, resulting in lower and lower prices. As well as being able to order online, customers can now buy themselves an ‘over the counter’ DNA test kit in stores such as Superdrug, which sells 23andMe health and ancestry tests. Whether you buy online or over the counter, purchasing a home DNA kit has become as convenient as getting groceries.

What can I use a home DNA test for?

The most popular DNA tests are for ancestry analysis. These are easy to buy online, and can tell you about your ethnic background up to around 10 generations back. These tests often come with an optional family finder feature, which will allow you to connect with relatives all over the globe. Some ancestry tests will come with additional analyses, like genetic health information, or how much Neanderthal DNA you have.

Genetic health tests are also rising in popularity. Some of these will tell you your genetic predispositions to certain diseases or conditions, while others provide diet and fitness recommendations based on your genetic profile, even tailoring meal plans and fitness regimens for you. These tests sometimes allow you to upload your genetic data file from an ancestry DNA test you’ve already taken – making it unnecessary to purchase a new DNA test.

DNA tests for familial relationships are also quite common. These can settle disputes over paternity, reunite lost relatives, and confirm biological relationships between other close relations, like grandparents, aunts and nephews, and first cousins.

What’s included in a home DNA testing kit?

What you’ll receive in your DNA kit depends largely on the type of test you take. Most of the DNA tests you can take at home will only require a cheek swab or saliva sample (e.g. a paternity test). Prenatal paternity or foetal sex tests will require a sample of the mother’s blood, which will have to be collected by a medical practitioner. The equipment you are provided with and the extent to which these tests can be considered “home” DNA kits therefore varies quite a bit.

Different genetic testing companies will have different preferred methods for sample collection. Some companies will send you a cheek swab (that looks like a cotton bud), while others might send you a cheek scraper (which looks and feels a bit like a soft bristled toothbrush). Many ancestry testing companies will send a small container for collecting a saliva sample. All three methods allow you to collect a sample containing a sufficient volume of DNA, and all three are commonly used for DNA testing.

DNA kits that rely on saliva collection will usually contain a solution to add to the sample. This is intended to preserve and protect the DNA, ensuring it doesn’t degrade or get contaminated before it reaches the lab. All you have to worry about is making sure the sample container is properly sealed, and there will usually be instructions about this in the kit. Many testing companies (but not all) will also provide return packaging for sending back your samples.

Is a blood sample more accurate?

When you are testing your own DNA, e.g. for an ancestry or paternity test, giving a blood sample is no more accurate than submitting a cheek swab or saliva sample. Genetic testing companies prefer to ask for cheek swab or saliva samples since these are easier to take, are less messy, and are less daunting for customers. Your DNA can be found in nearly every cell in your body, and so – in terms of accuracy – whether the sample given is blood, saliva or cheek cells makes no difference.

For prenatal tests, such as prenatal paternity tests or foetal sex tests (sometimes called “baby gender tests”), it will be necessary for the mother to provide a blood sample. This is because these tests look for Cell-Free Foetal DNA (shortened to cffDNA or cfDNA) belonging to the unborn child. For prenatal paternity tests, the cffDNA is compared to a DNA sample given by the potential father (often a cheek swab sample) to test for paternity. Prenatal sex tests look only for the presence of a Y chromosome, which would indicate a boy. If no Y chromosome is found, it is assumed the baby is a girl.

Please bear in mind that blood samples for prenatal DNA tests must be taken by a trained medical professional. Any test that allows you to collect your own sample at home will not yield accurate results.

What about pet DNA testing?

DNA kits for testing your dog’s DNA are surprisingly similar to those used for human DNA tests. Most will include a mouth swab, which you can use to collect a cheek cell sample from your pet’s mouth. This is just as painless for them as it is for humans, and means that in most cases, the tests are suitable for puppies as well as full grown dogs. As with kits for humans, dog testing kits will come with instructions. The website for Embark, which tests your dog’s DNA for breed ancestry and genetic health markers, also includes a video showing how to swab your dog’s mouth.

Cat DNA tests are newer than those for dogs, and so the information you can learn about your feline friend is a bit more limited. The kit for collecting your cat’s DNA from Basepaws usually contains strips for collecting samples of your pet’s fur: something they are bound to enjoy. If, however, you have a hairless cat, such as a Sphinx, you can check a box when ordering to request a cheek swab kit instead.

DNA kits for birds – which can be used to determine sex – usually require a few feathers or a small blood sample. These samples are so simple to collect that you don’t usually receive a physical home DNA testing kit, but rather are given instructions online for how to take the samples and send them to the lab.

How accurate are results from home DNA tests?

Familial DNA test accuracy

When purchasing DNA tests for familial relationships such as paternity, it is important to always check the company’s accreditations. If the company uses a lab accredited by ISO (International Organization for Standardization), their processing of your DNA samples should be done according to international standards. In the UK, companies selling familial DNA tests for legal or immigration purposes must be approved by the Ministry of Justice.

Family relationship tests between close relatives have extremely high degrees of accuracy. Paternity tests can confirm paternity with 99.99% certainty, and exclude potential fathers with 100% certainty.

Still, the private genetic testing industry is currently largely unregulated, and so you should try to do as much research on your chosen company as possible before making a purchase. When purchasing tests from companies based overseas, particularly outside of the EU, be aware that they may not be subject to the same regulations – and you may not be offered the same protections – as in your own country.

Ancestry DNA test accuracy

When purchasing a DNA testing kit for ancestry, it is best to go for a large company that you have heard of, such as AncestryDNA, 23andMe, MyHeritage, Living DNA, or Family Tree DNA. If you test with more than one company you should expect for your results to be slightly different, due to the number of people in each database, how well different ethnicities are represented in each database, and that company’s particular algorithm for assigning ancestry percentages to their users.

In 2018, AncestryDNA made a significant update to their service, adding new regions to their ethnicity results, and tuning their algorithm to provide more accurate ancestry percentages. Though this meant their service would be more reliable moving forward, many people were upset that their ancestry results had changed. For some people, particularly people of African heritage, the update meant they were unlikely to have the same genetic background as they had previously thought.

It is worth bearing in mind that although companies are able to provide ancestry estimates with ever increasing accuracy as their databases grow and their algorithms improve, their results are still only estimates. We do not have genetic samples from our fifth-great-grandmothers, and even if we did, it is possible we may not have inherited any DNA from her at all. Each person can only carry a limited amount of DNA, and so with every new generation, some DNA from previous generations is lost.

Health DNA test accuracy

Private genetic health tests provide results based on very new research that has yet to be repeated and consolidated by further studies. The most reputable providers will give you information on the research they based their findings on, and also about the specific genes they looked at, so that you can investigate further and assess how accurate their results are. The best providers will even evaluate their own research and grade the results they give you by how reliable the studies they’re based on may be. Providers of genetic health tests are often very careful about how they word their results due to the strength of the research the results are based on. Expect to see results like, “You are likely to…” or “People with your genetic variants often…”

The issue of accuracy and reliability is perhaps most significant with the tests that assess your genetic predisposition to certain diseases. Although these tests can often give you a good idea of the sort of conditions you are more genetically disposed to, they are far from a diagnosis. In some cases, the results may be misleading for customers who don’t realise that their “higher than normal likelihood” for developing a certain disease may be only 1% higher than average – i.e. still not very likely at all. This is because DNA testing purely assesses your genetic predisposition, whilst in reality, other biological and environmental factors play equally important roles.

How much do home DNA tests cost?

You may be wary of purchasing a home DNA test because of the price, though this is usually not as high as you might expect. As direct-to-consumer genetic testing has become more accessible to the public and easier for labs to perform on mass, the cost has decreased dramatically in recent years.

Prices differ depending on the type of test you wish to take, how much of your DNA is tested, and the number of genetic analyses and extra services that are provided. For instance, health DNA testing tends to be more expensive than paternity testing, since this usually includes detailed analysis of multiple genes, while paternity tests only compare repeating patterns in DNA that are hereditable.

Here’s what you can expect to pay for different testing types:

• Ancestry DNA tests: usually between £70 and £100

• Health DNA tests (diet and fitness): usually between £100 and £300

• DNA sequencing: usually between £2000 to £3000

• Paternity tests: usually around £100

• Prenatal paternity tests: around £1000 or more

• Prenatal sex tests: around £200

• Dog DNA tests: around £150

Be aware, if you buy a DNA testing kit in a store, you will have to pay an additional lab fee before they begin testing your sample. Rarely, this is sometimes also the case for the kits you buy online. Companies sometimes draw customers in with the promise of “free” DNA kits – the kit itself might be free, but the test won’t be.

The time it takes to get your results varies between tests. For paternity tests, you may get your results the next day. Health and ancestry tests take around six to eight weeks, while full DNA sequencing may take three months or more. For more information, see our article ‘How long does a DNA test take?’