The storage conditions for cell-free DNA (cfDNA) blood collection tubes may vary depending on factors such as the type of the tube, the manufacturer, and the additives contained therein. Generally speaking, the main aspects are as follows:

Temperature Conditions

• Refrigerated Storage: Usually, after blood collection with cfDNA blood collection tubes, they should be placed in an environment with a temperature of 2 – 8 °C for refrigerated storage as soon as possible. This temperature range helps to inhibit the activity of various enzymes in the blood, slow down the speed of cell metabolism and DNA degradation, and maintain the stability of cell-free DNA. For example, in some clinical studies and tests, it is strictly required that the blood collection tubes be placed in a refrigerator at 2 – 8 °C within 2 hours after collection to ensure the accuracy of test results.
• Avoid Freezing: Generally, it is prohibited to freeze cfDNA blood collection tubes. During the freezing process, the water in the blood will form ice crystals, which may damage the cell structure and the integrity of DNA. Meanwhile, it may also cause the components such as additives in the blood collection tubes to denature or precipitate, affecting the performance of the blood collection tubes and the test results.

Light Conditions

Cell-free DNA blood collection tubes should avoid direct sunlight and strong light irradiation. Ultraviolet light and other light rays may cause photolysis reactions of DNA, resulting in the destruction and degradation of the molecular structure of DNA. Therefore, during storage and transportation, it is best to place the blood collection tubes in light-proof containers or packages, such as black or brown sleeves for blood collection tubes or light-proof bags, to reduce the impact of light on cell-free DNA.

Time Limit

• Short-Term Storage: For most cell-free DNA blood collection tubes, under the refrigerated condition of 2 – 8 °C, it is generally recommended that the samples be tested or further processed within 24 – 48 hours after collection. During this period, the stability of cell-free DNA is relatively good, which can ensure the reliability of test results.
• Long-Term Storage: If long-term storage of cell-free DNA samples is required, the plasma or serum can be separated after collection, transferred to specialized cryopreservation tubes, an appropriate amount of DNA protectant added, and then stored in a low-temperature refrigerator at -20 °C or -80 °C. However, even under low-temperature conditions, cell-free DNA may still degrade to some extent as time passes, so the storage time should not be too long either.

Other Precautions

• Keep Dry: The blood collection tubes should be stored in a dry environment to prevent the growth of microorganisms on the surface of the tubes due to moisture, or to avoid the labels and markings on the tubes from becoming blurred, which may affect the identification and management of samples.
• Prevent Vibration: Severe vibration may cause the cells in the blood to rupture and release intracellular DNA, interfering with the test results of cell-free DNA. Therefore, during storage and transportation, every effort should be made to avoid the blood collection tubes from being subjected to severe vibration and collision.