By Katherine Lawless on September 23, 20202020-09-23
From sample collection to data analysis, it takes a lot of work to perform a successful genetics study. The quality of your DNA samples will affect the quality of your data. To ensure your sample quality is maintained from point of collection to processing in the lab, the key is sample stabilization.
What does it mean for a sample to be stabilized?
Sample stabilization provides:
- Reproducibility and Sample Homogeneity – DNA yield, quality and performance are the same across multiple aliquots taken from the sample at different time points
- DNA Integrity – prevents DNA degradation ensuring that the DNA remains of a molecular weight suitable for all downstream applications
- Prevention of microbial growth
Essentially, stabilization ensures that your DNA samples does not change over time. Without stabilization, the sample may not yield enough quality DNA to perform downstream assays.
[For more information on sample stability, visit our blog titled Stabilize your sample: A “right from the start” Q&A]
Here are 3 reasons why it is important to stabilize your DNA sample.
#1 Sample stabilization enables self-collection of samples by mail
Ensuring the saliva sample is immediately stabilized after collection is important in maintaining the quality of your DNA sample.
Blood was traditionally viewed as the standard for collecting high quality DNA, however studies point out that invasive venipuncture is the main reason for recruitment refusal. Additionally, most blood collection requires access to clinical infrastructure preventing donors from completing a self-collection in the comfort of their home.    Dry swabs can also be used when collecting samples at-home as an alternative to blood, however, without stabilization, dry swab samples are prone to bacterial growth and DNA degradation, rendering it unusable once it reaches the lab.  
Saliva collection kits containing stabilizing solutions, such as and , can simply and effectively stabilize DNA from saliva at room temperature for years. Since many collections are taking place at-home stabilizing the DNA in saliva is important to prevent chemical and enzymatic degradation of the DNA during transport to the lab.
#2 Sample transportation from donor to lab is commonly known to have temperature fluctuations and delays which can affect samples’ stability
Sample stability during transportation is important and can become very unpredictable with regards to temperature fluctuations and delays.
This is not a concern, however, when using products that immediately stabilize samples. Sample collection methods that rely on other methods, such as cold chain transportation, can be quite costly and difficult. In terms of transport, blood samples require dry ice, express/overnight shipping and multiple shipping containers, on average costing $80 USD per sample.   
[See our blog DNA saliva kits or traditional blood collection: which is more cost effective? For more information]
Samples collected into devices such as Oragene and ORAcollect have been validated for room temperature storage and are robust enough to endure temperature fluctuations that might be experienced during transport. Oragene/ORAcollect has been proven to withstand (3) multiple freeze-thaw cycles ranging from –20°C to +50°C ensuring, optimal sample stability during transportation without unpredictable difficulties. 
Collecting samples in-field – an example
Not all biological samples are collected from the comfort of someone’s home or in the clinic. Sometimes researchers must go to remote parts of the world and collect in the field. This means that there must be a way to keep the DNA samples stable across various conditions and temperature fluctuations when collecting in different climates. Collecting blood or raw saliva samples without a stabilizing reagent in these types of settings would require more expensive methods to keep the DNA sample stable, such as transportation frozen on dry ice.
Example: Hot climates
“The collection of saliva using the Oragene collection kit was easy and fast. The samples are quite stable in the field and while traveling back to the lab, even the high temperatures of that region (close to 35*C). Furthermore, our analysis on paired Oragene/saliva blood samples indicates no difference in DNA yield, quality and genotyping results.” Prof. Dr. Carlos Menck.
If raw, unstabilized saliva samples had been collected, the elevated temperatures encountered in the field during transport back to the lab would have led to significant microbial growth and possible putrefaction of the sample . Use of whole blood collection would have involved significant expense for dry ice and hazardous materials couriers.  
#4 Storing your samples long-term
Researchers often want to biobank collected DNA samples for future research. Some studies will store their donors’ samples for months or years.
Unstabilized samples may undergo changes if there is any delay between collection and freezing, although even an immediate freezing process at the point of collection is no guarantee of the sample’s safety. One risk involved with frozen samples is unexpected power failures.
Freezing samples also entails significant costs for equipment and energy. Saliva samples collected in and can be stored at ambient temperature thereby eliminating the expense and complexity associated with frozen samples.
Storing your sample for long-term storage
- Different studies   conducted to evaluate whether saliva samples collected in an Oragene kit could maintain DNA integrity at room temperature.
- For example: Anthonappa et al. (2012) found that Oragene did not reduce in quality of DNA when stored at room temperature for 18 months.
- Other studies conducted   , also showed that Oragene saliva samples can be stored for at room temperature for 4 to 5 years. Stored the saliva samples frozen between -20ºC to -80ºC with no change in the molecular weight of the DNA or the quality and could withstand 3 freeze-thaw cycles. 
Ensure your sample quality is maintained
Stability of your biological samples is important to ensure that your data and results are accurate and not biased. The best way to ensure your samples remain stable during transport and storage is to make sure you a have a reliable sample collection method that can effectively stabilize your DNA over long periods of time at ambient and elevated temperatures.
 Hansen et al. Collection of blood, saliva and buccal cell samples in a pilot study on the Danish nurse cohort comparison of the response rate and quality of genomic DNA. Cancer Epidermiol Biomarkers & Prevention. 2072-6 (2007).
 Galbete C et al. Lifestyle factors modify obesity risk linked to PPARG2 and FTO variants in an elderly population: a cross-sectional analysis in the SUN project. Genes Nutr. 8(1):61-67 (2013).
 Anthonappa et al. Evaluation of long-term storage stability if saliva as a source of human DNA. Clin Oral Invest 17:1719-1725 (2013).
 Davis R et al. Specimen collection within the CRN: a critical appraisal. CRN (2010).
 Karni et al. Thermal degradation of DNA. DNA and cell biology. 32. (2013) 10.1089/dna.2013.2056.