Pharmacogenomic (PGx) testing requires a DNA collection, for which there are two methods typically used: cheek swabs (buccal swabs) and saliva samples. Both are non-invasive and have their own pros and cons. According to a report shared by PubMed, cheek swab tests have proven to be more stable and resilient. Following is a deep dive into the cheek swab vs. saliva test:

Comparison of Saliva Test and Swab Test in Pgx Testing

1. Stability and Longevity Comparison

• Cheek Swab: Collects cells (from the inside of the cheek), which are nucleated (contain a nucleus). While saliva also contains nucleic acids, it may have less DNA and a higher chance of contamination.
• Saliva Test: Compared to a saliva test, a buccal swab may be a high-quality DNA source that is more resilient and stable over time. DNA extracted from cheek cells remains intact for longer periods, even with delays in processing or transport. Thus, cheek tests are better for long-term storage and retesting in PGx studies.

2. Comparison with Ease of Collection

• Cheek swab: Collection is straightforward and generally well-tolerated by most individuals. Just a gentle rub inside the cheek for a few seconds allows the collection of DNA. This process is quick, easy, and minimally uncomfortable.
• Saliva: This method can sometimes be difficult, particularly for individuals with dry mouth or older patients. However, saliva collection may be more convenient for patients who may be uncomfortable with cheek swabs or those who require multiple samples. Additionally, the ability to collect larger volumes of DNA can be beneficial in cases where a significant amount of material is needed.

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Transport and Storage Comparison

• Cheek Swabs (Buccal Swabs): Cheek swabs can be stored at room temperature – requiring no special storage conditions, such as refrigeration – cheek swabs provide easy stability during transport. Hence, making them ideal for long-distance shipping.
• Saliva: On the other hand, to maintain DNA, saliva samples require special storage conditions. They typically require refrigeration or the use of preservative agents to prevent microbial contamination or DNA degradation. Some newer saliva collection kits thus include DNA stabilizing agents, making them less sensitive to temperature fluctuations and improving the overall PGx saliva test accuracy.

Saliva and buccal tests both have their advantages and disadvantages. Your preferences should actually be based on your requirements. While a saliva test may provide sufficient DNA, as shared by the Chicago geneticist, for more complex genetic tests, a blood test may be required.

While cheek swabs and saliva tests differ in process, both contribute to overall testing expenses. See our detailed breakdown on PGx testing costs

When to Use Each Method: Cheek Swab vs Saliva Test

The choice between a cheek swab and saliva test depends on DNA purity, sample stability, contamination risk, cost, ease of use, and regulatory compliance. Privacy, data security, and risks of inaccuracy (e.g., false positives from food remnants) must also be considered.

Choose a Cheek Swab if:

• High purity and stability of DNA are needed in order to be able to perform accurate genetic analysis and ensure minimal bacterial contamination.
• The testing is done in a controlled clinical or forensic environment, and reliability is provided through professional supervision.
• The sample provided is a child, an old person, or a person with a dry mouth condition, thereby making it difficult to produce saliva and raising questions of low yield.
• Stability in transport and storage is essential, particularly in long-distance shipping, which is not refrigerated, which concerns the logistics, such as sample degradation.

Choose a Saliva test if:

• More DNA is required to be analyzed in more depth, e.g. a whole-genome sequencing, but this puts a person at greater risk of contamination by oral bacteria or recent food.
• It specialises in convenient at-home or direct-to-consumer genetic testing kits with an emphasis on convenience and accessibility, as well as in data management and user privacy.
• Comfort must be as non-invasive as possible, which is good when conducting a screening on a large scale, although there is a concern that the quality can be inconsistent unless obtained in a superior manner.

In the majority of genetic testing applications, such as ancestry, health diagnostics, or drug screening, the two approaches are both valid and reliable.

Cheek Swab vs Saliva Swab Comparison Summary

• Purpose: Cheek swabs mainly prepare genetic material (DNA), whereas saliva tests prepare a range of substances and molecules in oral fluid.
• Collection: The two are both non-invasive, yet the cheek swab isolates cells on the inner cheek, and a saliva test is a spit sample.
• Application: Cheek swabs tend to be better in a genetic analysis because they are more stable. In drug testing, the saliva is used the detect substances in the system.

Conclusion

Both cheek swabs (buccal swabs) and saliva tests have their own pros and cons. Cheek swabs provide more resilient, high-quality DNA with low contamination risk and greater stability, making them ideal for long-term storage and reliable results. Saliva tests, on the other hand, are flexible and can provide larger volumes of DNA, making them ideal in certain contexts where higher sample quantities are required.

Disclaimer: This blog is for informational purposes only and does not constitute medical, legal, or professional advice. While we strive for accuracy, errors or omissions may occur. Some images in this blog may be AI-generated or for illustrative purposes only.