The specific application process of the cell – free DNA blood collection tube is as follows:

I. Preparation Stage

1. Inspection of the Blood Collection Tube
   • Check whether the packaging of the cell – free DNA blood collection tube is intact. Ensure that the blood collection tube is not damaged during transportation and storage, such as checking whether there are cracks in the tube body and whether the cap is well – sealed.
   • Verify the expiration date of the blood collection tube and avoid using expired ones to ensure the effectiveness of the protective substances and coatings inside the tube.
2. Preparation of Blood – drawing Equipment
   • Prepare a suitable blood – drawing needle. The specification of the blood – drawing needle should be selected according to the patient’s condition and the difficulty of blood drawing. For example, for children or patients with thin blood vessels, a thinner blood – drawing needle may be needed.
   • Prepare auxiliary blood – drawing supplies such as tourniquets, disinfection cotton balls, or alcohol swabs. The tourniquet is used to make the veins bulge for easier blood drawing, and the disinfection supplies are used to disinfect the blood – drawing site to prevent infection.

II. Blood – drawing Stage

1. Patient Preparation
   • Explain the purpose and process of blood drawing to the patient to relieve their nervousness. The patient’s psychological state may affect the blood – drawing process. For example, excessive nervousness may lead to vasoconstriction and increase the difficulty of blood drawing.
   • Have the patient in a comfortable position, usually sitting or lying down, and keep the limb for blood drawing relaxed. A proper position is helpful for smooth blood drawing. For example, the arm for blood drawing should hang naturally or be placed on a stable support.
2. Disinfection of the Blood – drawing Site
   • Select an appropriate blood – drawing site, usually the veins of the upper limb, such as the median cubital vein. Use a disinfection cotton ball or an alcohol swab to wipe and disinfect in a spiral pattern outward from the blood – drawing point. The diameter of the disinfection range is generally not less than 5 cm, and blood drawing is carried out after the alcohol has evaporated.
3. Blood – drawing Operation
   • Tie a tourniquet about 6 – 8 cm above the blood – drawing site with an appropriate tightness, which should be able to block venous blood flow but not affect arterial blood flow. Generally, the tourniquet should not be tied for more than 1 minute to avoid long – term blood stasis affecting the test results.
   • According to the principle of aseptic operation, insert the blood – drawing needle into the vein to let the blood flow into the cell – free DNA blood collection tube. During blood drawing, keep the blood collection tube in a vertical position to ensure smooth blood flow into the tube and avoid air bubbles. The amount of blood drawn is determined according to the requirements of the test items, generally between 2 – 10 ml.

III. Post – blood – drawing Treatment Stage

1. Treatment of the Blood Collection Tube
   • After blood drawing is completed, immediately release the tourniquet, withdraw the blood – drawing needle, and press the blood – drawing site with a disinfection cotton ball to stop bleeding. The pressing time is generally 3 – 5 minutes.
   • Quickly close the cap of the blood collection tube tightly to ensure sealing. Then gently invert the blood collection tube 8 – 10 times to make the blood fully mix with the protective agents and anticoagulants inside the tube to prevent blood coagulation and degradation of cell – free DNA.
2. Sample Labeling
   • Label relevant patient information on the blood collection tube, including name, gender, age, hospital number (if any), date and time of blood drawing, etc. Accurate labeling information is crucial for sample identification and subsequent testing to avoid sample confusion.
3. Sample Storage and Transportation
   • According to the requirements of the blood collection tube manufacturer, store the blood collection tube in an appropriate temperature environment. Generally, the samples in the cell – free DNA blood collection tube can be stored short – term at 4 – 25 °C.
   • If sample transportation is required, put the blood collection tube into a special transportation container. Ice packs or other constant – temperature materials can be placed in the container to ensure that the sample temperature remains stable during transportation and prevent sample deterioration. During transportation, pay attention to avoiding severe vibration and collision to protect the integrity of the sample.

IV. Testing Stage (Conducted in the Laboratory)

1. Sample Reception and Verification
   • After the laboratory receives the sample, first check whether the labeling information on the blood collection tube is consistent with the submission form and check whether the blood collection tube is damaged or leaking.
   • Record the reception time and status of the sample to ensure that the process from sample collection to testing is traceable.
2. Sample Processing and Testing
   • According to the requirements of the testing method and equipment, further process the sample, such as centrifugation, extraction of cell – free DNA, and other operations.
   • Analyze the cell – free DNA using professional testing equipment and techniques, such as detecting specific gene mutations or disease markers through polymerase chain reaction (PCR), gene sequencing, and other methods to obtain the data required for diagnosis or research.