DNA: How do we collect DNA from your saliva sample?

We at BioCertica, extract your DNA from your saliva sample provided in our user-friendly, at-home sample collection kit.

Genetic Tests

Recently, we have been writing about genetic tests, their importance, and their applications. Although explained as a simple process of looking for changes within your genetic material,  genetic testing is a complex and step-wise process, from sampling to DNA extraction and various quality checks to finally obtaining and analyzing results. Therefore, we divide the procedure into the following steps:

• Sample collection
• DNA extraction
• DNA quality control, storage, and management
• Genotyping using the microarray
• Obtaining and analyzing genotyping results
• Generating report

Sample Collection

In this article, we will elaborate on the process of saliva sample collection. Firstly, let's give a definition of DNA sampling. Most importantly, DNA sampling represents the method of obtaining biological material to undergo further DNA procedures and analyses (firstly DNA extraction, followed by ancestry or genealogy testing, paternity testing, and genetic screening for diseases…). 

It is the first and most crucial step in conducting research or performing any analysis in molecular biology. The sample collection technique mainly depends on a sampling DNA kit [1, 2].

How do we collect DNA samples?

There are several ways of collecting DNA samples. DNA can be obtained from all living material: tissue, nail, blood, saliva, semen, or hair. Here we explain the procedure behind saliva sample collection, as we at BioCertica rely on it.

Saliva, also known as spit, is an extracellular fluid in the mouth produced by salivary glands. Human saliva consists of 98% of water but also contains electrolytes, mucus, enzymes, antimicrobial agents, lysozymes, and most importantly for us to collect your DNA: epithelial cells (cheek cells) and white blood cells [3].

BioCertica DNA kit

At BioCertica, our procedure starts when you order one of our DNA kits. Within your ordered DNA kit, you will find a QR code link with detailed, step-wise instructions to help you give a good-quality saliva sample [4]. It is very important to read the instructions before providing a sample. 

The kit includes a mouthpiece attached to a tube containing a stabiliser to keep your saliva sample clean and prevent DNA degradation. Additionally, you are provided with a blue cap to seal the tube once you've provided your sample. Lastly, a sample bag is provided to place your sample tube in, along with a plastic container to safely seal your sample for the journey to the lab. 

Providing a DNA saliva sample

Firstly, before providing a sample, make sure to read the instructions provided.

In order to give a high DNA-yielding sample, softly, use your fingers to rub your cheeks against your teeth, thus releasing cheek cells containing DNA into your saliva. Then, spit the saliva from your cheek into the tube until you reach the line indicating that have provided a sufficient volume. After collection, the samples are sent via couriers to the laboratory for DNA extraction and testing.

What should you pay attention to before and after sample collection?

It is crucial to ensure your sample integrity and quality are maintained during the whole sampling procedure. It is essential to follow these guidelines to ensure a sufficient amount of DNA. Here are several notices you should remember to provide the lab with enough quality DNA samples for genotyping and analysis [5, 6].

Steps to follow

1. The best practice is to collect your sample in the morning 30 minutes after brushing your teeth. During those 30 minutes, refrain from eating, drinking, smoking, and chewing gum.
2. Do not remove the plastic film from the funnel lid that contains the clear liquid. 
3. Make sure you do not touch the tips of the funnel lid to avoid contamination. Also, do not put it on a contaminated surface. However, if you are collecting a sample from someone else, you have to be careful since you could contaminate the sample with your DNA.
4. Do your best to provide enough saliva (not including foam/bubble) to reach the “Fill to” line before you close the lid of the funnel. Let the foam settle before you close the lid or it will overflow.
5. You should not re-open the tube and add more saliva once you close the funnel.
6. Do not rest the tube on a tabletop when it is open, as it will tip over. Instead, place it upright in a glass if you need to put it down.
7. Before spitting, relax and rub your cheeks gently for 30 seconds to make enough saliva. 
8. If you find it difficult to produce enough saliva, place a very small amount of white table sugar on your tongue. 
9. Do not ingest the liquid in the funnel. Wash with water if liquid comes in contact with your eyes or skin.
10. Follow the packing and shipping instructions provided within the DNA kit. 
11. Environmental conditions such as sunlight, high temperatures, moisture, and chemicals may damage samples and degrade DNA. Therefore, the best practice is to order the courier to pick up your sample on the day of collection. 

Here is a short video if you would like to see how it practically works.

What are other methods of sample collection?

As mentioned, DNA is not only collected from saliva. It can also be collected from many sources, including blood, buccal cells, semen,­ nails, etc. 

Buccal swabs

The inner part of our mouths is rich in squamous epithelial cells. These cells are often called cheek cells, and they take approximately 5-12 days from production to detachment from the epithelial surface. Therefore, they are easy to obtain by mouth rinse or simple swab, making them the perfect tool for obtaining and analyzing an individual’s genetic makeup [7]. 

To take a buccal sample, remove the swab from the packaging and rub it on the inside of one of your cheeks for 45 seconds. Then, seal the vial and repeat the procedure with the other swab on the other cheek. Buccal Kits often contain more than one swab as a backup sample, in case the first swab does not have enough DNA or the DNA quality is compromised.

Previously at BioCertica, we relied on swab samples. However, now we make use of the saliva samples due to the following reasons: 

• Saliva samples provide sufficient DNA quantity and better quality for genetic testing purposes, compared to buccal swabs.
• Buccal swabs need to be processed rapidly to have an appropriate DNA yield while saliva samples contain DNA stabilisers to allow for longevity. 
• Saliva samples are easier to handle and less invasive [8]. 

Blood sample

Blood samples are collected in two ways, in blood tubes or FTA (Finger Technology Association) cards [9, 10].  The tubes used for blood collection usually contain anti-clotting agents to prevent the degradation of the sample. Blood samples collected in tubes are obtained through needle aspiration. 

Another method is to use FTA cards, which are chemically treated, cotton-based filter papers designed to collect, preserve, and ship biological samples like DNA. In this method, DNA is trapped and adhered to the paper.

What after sample collection?

The first step is to sign up in the BioCertica mobile application. Then you should follow a sequence of steps, easy as the ABC depicted below (Figure 4).

As depicted above, after completing the sample collection, you will need to activate your test kit online at BioCertica mobile app by scanning the QR code on your camera phone. You will immediately get instructions on how to register your kit.

Upon registration, you will need to schedule a courier to pick up your samples and deliver them to the lab as soon as possible. After this, our team will reach out to you via e-mail and send you a lifestyle questionnaire. 

Figure 5: BioCertica DNA saliva sample

Finally, you will get results within 4 to 6 weeks after sample collection. Of course, we will notify you once your results are ready! Do not wait! Order your kit now here! 

Written by: Nermin Đuzić, M.Sc. in Genetics, Content Specialist

Peer-reviewed by: Edin Hamzić, Ph.D in Genetics, Chief Scientific Officer & Lomari Geertsema, M.Med.Sc in Human Molecular Biology, Laboratory Analyst

References

1. Mullegama, S. V., Alberti, M. O., Au, C., Li, Y., Toy, T., Tomasian, V., & Xian, R. R. (2019). Nucleic acid extraction from human biological samples. Biobanking, 359-383.
2. National Research Council. (1998). Evaluating human genetic diversity.
3. Young, J. A., & Schneyer, C. A. (1981). Composition of saliva in Mammalia. Australian Journal of Experimental Biology and Medical Science, 59(1), 1-53.
4. Granger, D. A., & Taylor, M. K. (Eds.). (2020). Salivary bioscience: foundations of interdisciplinary saliva research and applications. Springer Nature.
5. Butler, J. M. (2010). Chapter 4—sample collection, storage, and characterization. Fundamentals of forensic DNA typing, 1st edn. Academic Press, San Diego, 79-97.
6. Center for Birth Defects Research and Prevention (2013). How to collect saliva (spit) samples for parents? Retrieved from: draft_salivainstructionsparent_engtest.pdf (cdc.gov)
7. Lee, E. J., Patten, G. S., Burnard, S. L., & McMURCHIE, E. J. (1994). Osmotic and other properties of isolated human cheek epithelial cells. American Journal of Physiology-Cell Physiology, 267(1), C75-C83.
8. Saliva vs swab test - what's the difference? (2021). Retrieved from https://www.testingforall.org/saliva-vs-swab-test-whats-the-difference/ 
9. Guha, P., Das, A., Dutta, S., & Chaudhuri, T. K. (2018). A rapid and efficient DNA extraction protocol from fresh and frozen human blood samples. Journal of clinical laboratory analysis, 32(1), e22181.
10. da Cunha Santos, G. (2018). FTA cards for preservation of nucleic acids for molecular assays: a review on the use of cytologic/tissue samples. Archives of pathology & laboratory medicine, 142(3), 308-312.