There are many precautions to note during the use of cell – free DNA blood collection tubes, covering all aspects before, during, and after blood collection. The details are as follows:

Before Blood Collection

• Selection of Blood Collection Tube
  Select the appropriate type and specification of cell – free DNA blood collection tube according to the detection project and requirements. Blood collection tubes from different manufacturers may vary in additive components, preservation performance, etc. Ensure that the blood collection tube is compatible with the subsequent detection methods and instruments.
• Patient Preparation
  Fully explain the purpose and process of blood collection to the patient to relieve their nervousness, as excessive nervousness may cause changes in blood components. Meanwhile, understand the patient’s diet, medication, etc. Certain medications or special diets may affect the detection results of cell – free DNA. If necessary, instruct the patient to stop taking medications or adjust their diet in advance according to the detection requirements.
• Inspection of Blood Collection Tube
  Carefully check the blood collection tube before use for any damage, cracks, or abnormal additives. If there are any problems, replace it promptly to ensure the quality and performance of the blood collection tube.

During Blood Collection

• Blood Collection Technique
  The blood collector should be professionally trained to master the correct blood collection technique and strictly follow the aseptic operation principle to prevent contamination during blood collection. Generally, venous puncture is used for blood collection. Ensure a smooth blood collection process to avoid repeated punctures that may cause hemolysis.
• Blood Collection Site
  Venous blood collection is usually preferred, and common sites include the median cubital vein. In special cases, such as for children or obese patients, other suitable veins can be selected according to the actual situation. Avoid collecting blood from the same limb where infusion or blood transfusion is taking place to prevent affecting the test results.
• Volume of Blood Collection
  Collect an appropriate amount of blood strictly according to the requirements of the blood collection tube. Both excessive and insufficient blood volume may affect the test results. Generally, the blood volume for cell – free DNA blood collection tubes ranges from 2 to 10 milliliters. Specifically, refer to the instructions of the blood collection tube.
• Order of Blood Collection
  If multiple types of blood specimens need to be collected simultaneously, pay attention to the order of blood collection to avoid interference between the additives in the blood collection tubes. Generally, collect the blood collection tube without additives first, and then the ones with additives. The cell – free DNA blood collection tube is usually collected in the middle order.

After Blood Collection

• Mixing and Standing
  Immediately after blood collection, gently invert the blood collection tube 5 – 10 times to fully mix the blood with the additives, ensuring the effective protection and stabilization of cell – free DNA. However, avoid violent shaking to prevent hemolysis. Some blood collection tubes may need to be left standing for a certain period, and the specific operation should follow the instructions.
• Storage and Transportation
  Cell – free DNA blood collection tubes generally need to be stored at 4 – 8°C. If the test cannot be carried out in a timely manner, store them according to the specified time and conditions. Use professional cold – chain transportation equipment during transportation to ensure a stable temperature and prevent the impact of temperature fluctuations on cell – free DNA. At the same time, ensure that the blood collection tube is not collided or squeezed during transportation to avoid damage.
• Testing Time
  Perform the test within the specified time after blood collection, preferably within 24 hours, to ensure the accuracy of the test results. Different types of blood collection tubes and detection projects may have different requirements for the testing time, which should be strictly followed.