Collection of Blood Specimens: A Comprehensive Guide
Blood specimen collection is a critical aspect of healthcare and laboratory procedures. Proper techniques are essential to ensure accurate test results and minimize patient discomfort. This comprehensive guide provides detailed information on the collection of blood specimens, including the equipment needed, preparation, procedure, and safety considerations.
Equipment and Supplies:
- Venipuncture Needle: Choose the appropriate gauge needle based on the patient’s age, vein condition, and the intended tests. Common gauges include 21G, 22G, and 23G.
- Vacutainer Tubes: Use vacuum-sealed tubes for blood collection. The choice of tubes depends on the tests being conducted.
- Needle Holder: A device to secure the needle in place during the procedure.
- Tourniquet: A tourniquet is used to dilate veins and make them more visible and accessible.
- Alcohol Swabs: To clean the skin and reduce the risk of infection.
- Gloves: Wear disposable gloves to maintain a sterile environment and protect yourself and the patient.
- Cotton Balls or Gauze: For applying pressure to the puncture site post-collection.
- Adhesive Bandages: To cover the puncture site and prevent bleeding or infection.
- Labeling Materials: Ensure proper identification of specimens with labels, including patient name, date, time, and other necessary information.
- Make the patient to sit comfortably in the phlebotomy chair. Identify the patient by asking his particulars and compare them with the request form.
- Inform the patient about the specimens to be collected. Always ask if he or she has undergone blood tests previously. In case of any history of abnormal reactions to blood collection, inform MO I/C lab/Pathologist before phlebotomy and then follow his instructions.
- Thoroughly check the request form for the number and type of the investigations. Prepare proper labels and paste them on appropriate containers before obtaining specimens. In case of any doubt, check the authenticated test list where information regarding type, quantity, preservative and storage of the specimen is given for various blood tests. If still there is any doubt, ask the senior colleague/NCO/JCO in-charge or the Pathologist.
- Select syringe of appropriate size so that the quantity of blood required can be obtained in single prick. If multiple samples are required, or >15 ml of blood is to be collected use a butterfly needle or a canula.
- Select appropriate vein (preferably antecubital) from forearm. Cleanse the skin over the venepuncture site in a circle approximately 5 cm in diameter with 70% alcohol/spirit swab, scrubbing the area vigorously.
- If the sample is to be collected for blood culture then skin is to be thoroughly sterilised rather than simple cleansing. Follow the procedure as under:
- Starting in the centre of a circle apply 2% iodine (or povidone-iodine) in ever- widening circles until the entire chosen area has been saturated with iodine.
- Allow the iodine to dry on the skin for at least 1 min.
- Completely remove1 the iodine with 70% alcohol/spirit swab following the pattern of application.
- Apply a tourniquet tight enough to obstruct venous flow only and relocate the vein to be punctured but don’t touch the proposed site of needle entry or the needle itself. Ask the patient to clench the fist to make the veins prominent. If the vein is not visible, palpate it with fingers. In case the veins of forearm are not visible/palpable, other sites such as dorsum of the hand may be selected.
- Insert the needle into the vein and withdraw blood till the required quantity of blood is obtained. Do not try to withdraw the piston too forcefully (hard pulling) as it can collapse the vein and it may cause frothing/ haemolysis of the specimen.
- Release the tourniquet once the needle has entered the vein.
- Apply pressure with thumb on antiseptic swab at puncture site for 2-4 min till the blood ooze stops. Only then patient should be allowed to move away from the specimen collection chair. The antiseptic swabs should be disposed off in designated baskets.
- Remove the needle from the syringe.
- The blood from syringe is distributed to appropriate, labelled containers.
- Inform the pathologist promptly under the following circumstances:
- If patient feels unwell after specimen collection, ask him to lie down on couch, reassure and give him hot drink.
- Some patients collapse when the skin is punctured or at the sight of blood. In such cases withdraw the needle immediately and ask the patient to lie down in supine position. Raise the legs of the patient.
- If specimen is not drawn in first prick.
- In case of children below the age of one year.
- In case of very sick patients/special blood specimen collection.
Blood Specimen for Serology:
Serological tests are required in most of the bacterial, viral and parasitic diseases. A clotted blood specimen is preferred.
- A vacuum collection system is both convenient as well as reliable.
- Paired specimens are to be collected during acute and convalescent phases of illness in certain viral and other infections to document a diagnostic rise in antibody titre.
- Protect blood specimens from extremes of heat and cold during transport.
- Specimens must be refrigerated. Whole blood is to be stored at 4°C. Serum can be frozen at -20°C or lower temperature and can be sent frozen to the reference laboratory.
- Sera for serology cannot be kept below 0°C, instead should be kept at 2-8°C.
Blood Specimen for Culture:
- Contact microbiologist/pathologist for appropriate media for blood culture, as the media may vary depending upon the type of pathogen suspected.
- Wash the hands with soap and water and wear sterile gloves.
- Withdraw the blood following the procedure described above.
- Change needle before injecting the blood into the culture bottle.
- Thoroughly clean the rubber bung of the culture bottle with iodine solution and inject an amount of blood equal to 10% of the volume of medium (for 30 ml medium 3 ml blood and for 50 ml medium, 5 ml blood is needed).
- After the needle has been removed, the site should be cleaned with 70% alcohol/spirit swab again.
- Don’t store the containers and caps separately.
- Blood obtained for culture of suspected anaerobes should not be exposed to air in any way.
- Needlestick Prevention: Always use needle safety devices to prevent accidental needlestick injuries.
- Infection Control: Adhere to infection control practices, including proper hand hygiene, personal protective equipment (PPE), and disposal of biohazard materials.
- Patient Comfort: Ensure the patient is comfortable and informed throughout the procedure.
- Waste Disposal: Follow guidelines for the disposal of biohazardous materials and sharps.
Proper blood specimen collection is crucial for accurate diagnostic and medical testing. It is essential to follow these guidelines to ensure patient safety and reliable test results.