Swabs vs. blood samples for DNA testing

Thanks to advancements in genetics over the years, DNA testing has never been more accessible or easy to perform using different sample types.

One of the most critical parts of the DNA testing process is the sample collection method. Samples for DNA testing must be collected in a way that minimises contamination risk and preserves the sample so that it can be transported to the laboratory without degrading. 

As DNA can be obtained from many different sample types, knowing what sample collection method to use for your DNA test can be confusing. In this article, we discuss two of the main sample collection methods – cheek (buccal) and blood sample collections – and which is the best sample collection method for your particular DNA test.

Cheek swab sample collection

A buccal (cheek) sample collection is a non-invasive sampling method. Most of our DNA relationship tests are conducted with DNA that has been collected using buccal swabs. 

Taking a DNA sample for one of our DNA tests is quick, easy and pain-free. 

To collect a buccal sample, take one swab and rub it firmly on the inside of your left cheek for at least 20 seconds. 

Use the second swab provided and rub it firmly on the inside of your right cheek for at least 20 seconds.

It’s important that you use both swabs to collect your samples to ensure that you have collected enough DNA. 

After you have used each swab, put both swabs straight into the sample envelope, with each swab facing in the same direction. Ensure the envelope is sealed and the information on the front of the envelope is completed fully, before posting your samples back to the laboratory. 

How does it work?

DNA is found within the nucleus of almost every cell in your body, including your cheek cells. Your DNA contains all the genetic information needed for your body to function.  

The DNA collection method works by collecting cells from the inside of your cheek. The cells on the inside of your cheek are constantly shedding, so the swab can quickly and effortlessly collect lots of cells. 

The cells you collect, containing your DNA, stick to the swab. 

When your sample arrives at the laboratory, we extract the DNA from the swabs using a process that breaks down the cells and releases the DNA. 

Once the DNA has been released from the cells, it is then analysed using a genetic analyser. We can then compare the DNA profiles we have obtained to see how likely it is that two (or more) individuals in the test are related (e.g. the likelihood that the potential father is the true biological father of the child). 

 To read more about our DNA testing process, read our DNA Science article here. 

Advantages

There are many advantages to the cheek swab sample collection method:

• Non-invasive and completely painless
• Quick and easy to perform on yourself or on others 
• Cheap
• Can collect samples in the comfort of your own home
• DNA collected on buccal (cheek) swabs can potentially be preserved for longer than some other sample types

Disadvantages

There are potentially some disadvantages to a swab sample collection, although most of these are easily avoided if samples are collected properly.

 Some potential disadvantages include:

• Contamination risk 
• Recent food/drink consumption can interfere with the test
• Chance of putting the wrong swab in the envelope 
• Microorganism growth can interfere with the test 
• DNA on swab can degrade if left for a long time 

To avoid contaminating samples, you should collect your own samples. In cases where this is not possible, such as with a young child, every measure should be taken to ensure you do not contaminate their sample with your own DNA.

You should also avoid eating or drinking for about 30 minutes before taking the test. Residual food on the swabs can cause mould or bacteria to grow, which in turn can interfere with the test. 

You must not put your swab in a plastic or sandwich bag. The plastic stops the swabs from drying out, which can encourage microbial growth. The growth of microorganisms can degrade the DNA, meaning we are less likely to obtain a result from your sample.

Don’t collect your sample if you are not ready to send it back to the laboratory immediately. The DNA can begin to degrade after a while, which may impact our ability to obtain a usable profile from the sample. 

There are some easy rules you should follow when collecting your buccal swab sample:

DO:

• Wash your hands before you collect your sample
• Wear sterile, disposable gloves if available 
• Remove any lipstick/lip gloss before collecting your sample
• Put your swabs straight into the sample envelope after collecting your samples
• Place the swabs facing the same direction in the sample envelope
• If collecting someone else’s sample, hold the swab stick as far away from the swab end as possible 
• Send your samples back to the laboratory as soon as you have collected them

DON’T:

• Eat or drink 30 minutes before collecting your sample 
• Put your swab on a surface before or after sample collection
• Remove the swab from the sterile packaging until you are ready to collect your sample 
• Collect your sample from an area other than the inside of your cheek
• Place the swabs facing the opposite direction in the sample envelope
• Put the swabs in plastic or sandwich bags before putting them into the sample envelope

Blood sample collection

DNA can also be obtained from a blood sample. 

The most common and accurate blood collection method is a blood draw by a trained phlebotomist or nurse. This is called a venous blood sample because the blood is taken directly from a vein. 

DNA can also be obtained from capillary blood. Capillary blood is usually obtained using a finger-prick method and can be done at home without the need of a phlebotomist or nurse. The capillary blood sample is usually collected using a small device called a lancet. The lancet contains a needle that pierces the skin when you eject it. 

How does it work?

Blood is a good source of DNA. The DNA in our blood is contained in leukocytes (white blood cells).

Depending on the type of test required, the blood is processed differently. At AlphaBiolabs, we only require a blood sample for our prenatal tests. The extraction process for our prenatal paternity test and prenatal gender test is more complex than our buccal swab extraction method.

When you are pregnant, some DNA from the unborn baby circulates in your bloodstream. This is called cell-free foetal DNA (cffDNA). For prenatal DNA testing purposes, the DNA is obtained from plasma using a more complex method before the sample can be sequenced. 

Advantages

Some advantages to using a blood sample include:

• Venous blood samples are much less prone to contamination 
• It’s easier to see if enough sample has been collected 
• Relatively quick procedure 

Disadvantages

There are some potential disadvantages to using blood samples for a DNA test, such as:

• Blood sample collection is more invasive than a buccal (cheek) swab collection
• Some people can get light-headed when having blood taken
• If someone has had a recent blood transfusion, more than one DNA profile may be observed, making it more difficult to obtain an accurate result
• There is often a cost associated with the blood sample collection method 
• Blood samples have a relatively short shelf-life at room temperature, so samples need to be returned to the laboratory as quickly as possible

What DNA tests require a blood sample?

At AlphaBiolabs, only our non-invasive prenatal paternity (NIPPT), and prenatal gender tests require a blood draw. 

Blood tests are required for our prenatal DNA tests because cell-free DNA from the foetus circulates in the bloodstream of the pregnant mother. 

Cell-free DNA from the unborn baby is usually found in your blood if you are more than 7 weeks pregnant. 

Our prenatal DNA tests are non-invasive, so collecting the sample won’t harm your baby.

If you are having a prenatal paternity test, only the mother is required to provide a blood and buccal (cheek) sample. The potential father just needs to provide a buccal sample. 

All of our other DNA tests, such as paternity, sibling or Y chromosome tests, do not require blood samples. For these tests, only buccal samples are required.

Which collection method should be used?

The collection method used depends on the type of test you need. 

At AlphaBiolabs, the two main methods of sample collection are buccal (cheek) swabs and blood samples. The sample collection kit you receive depends on the test you have ordered. 

We provide a buccal swab sample collection kit for the following tests:

• Paternity
• Maternity
• Sibling
• Twin 
• Aunt/Uncle 
• Grandparent
• Y chromosome
• Single genetic profile 
• Ancestry 

These tests only require a buccal swab because the sample needed to perform these tests can easily be collected from the inside of your cheeks. 

Samples for all of our peace of mind tests can be collected in the comfort of your own home. 

We provide a blood sample collection kit for the following tests:

• Non-invasive prenatal paternity (NIPPT)
• Non-invasive baby gender test

These tests require blood to be drawn because we are looking for the unborn baby’s DNA. This foetal DNA is found circulating in the pregnant mother’s blood.

Are there any other DNA sample collection options?

There are some other types of DNA samples, all with their own advantages and disadvantages.

DNA can be recovered from hair samples. Whilst some DNA can be found in the hair shaft, it is usually very degraded. Most of the ‘intact’ DNA is found in the hair root. For relationship testing purposes, it is very hard to obtain enough hair with roots to obtain a DNA profile. DNA from old hair (e.g. hair that is left on a brush) is also likely to suffer degradation. It is much easier to submit a buccal (cheek) swab sample.

You can also look for DNA on things like cigarette butts, ear buds, used tissues, teeth and bones. 

Forensic labs that examine evidence will analyse a wide range of different sample types such as those listed above. How successful the laboratory is at obtaining a DNA profile depends on the amount of DNA on the sample, how old the sample is, and how preserved the sample (and therefore the DNA) is. 

If you want to know more about the different types of samples we can analyse, contact our friendly Customer Services team on 0140 29466, or email us at info@alphabiolabs.ie

Where can I buy a DNA test?

We offer a comprehensive range of DNA tests to suit a variety of needs, with all testing carried out at our award-winning, accredited laboratory.

Our DNA testing services include parental DNA tests (paternity and maternity), prenatal DNA tests, sibling DNA tests, twin DNA tests, grandparent DNA tests and avuncular (aunt and uncle) DNA tests.

Simply place your order online and we will ship your test kit out to you in discreet, plain packaging, for full confidentiality.

We can also help you if you need a DNA test for official or legal matters.

For confidential advice on which DNA test is right for you, call our friendly and discreet Customer Services team on 0140 29466, or email us at info@alphabiolabs.ie