Collecting, storing, and analyzing DNA is a vital part of many medical fields and disciplines. To achieve viable results, regardless of the discipline, there is a need for high-quality and stable samples from which DNA can be extracted.
DNA is usually extracted from one of two primary sources: cheek cells or white blood cells. Cheek cell samples carry an increased risk of contamination by viruses, bacteria or environmental elements. Blood is, therefore, the preferred source of DNA samples.
Dried blood samples do not have the same time and temperature constraints as wet blood samples. They can be collected more efficiently in the field and transported and stored for later DNA extraction without the need for refrigeration.
DNA has traditionally been extracted from dried blood using dried blood spots on filter paper. However, studies conducted using this method found that it often required labor-intensive protocols and multiple extraction steps, difficult to perform during field studies.
Another benefit of using dried blood spot sampling for DNA extraction is the longevity of DNA in dried blood. Several studies concluded that viable DNA was present in blood stains for several months.
These results show little variation even under increased temperatures and humidity. No significant difference was found in the quality of the DNA extracted where the blood stain was subjected to 93% relative humidity or to temperatures of 35°C. These tests were carried out over a period of at least three months with no significant degradation of the DNA when extracted.
Tests have also been carried out under laboratory conditions to assess the degradation of collected dried blood samples. The results showed no degradation of the DNA, regardless of extraction method, when samples were kept at 4°C over 24 hours.
Given the study outcomes, standard laboratory conditions, including the ability to significantly cool samples, are not essential to the stability or longevity of DNA in dried blood spots obtained via microsampling techniques.