Laboratory blood Samples collection, transportation and preservation

UNIT II

2.1 Laboratory Samples for detection of parasites: Collection, transportation, processing, and preservation of samples for routine investigations – Blood, Stool.

2.2 Concentration techniques: Principle and application of concentration techniques of stool for demonstration of ova and cysts.

Laboratory Samples Collection of Blood for detection of parasites

The following three methods are used to collect blood samples for detection of parasites. The exact procedure and requirements depend upon specific parasite detection.

1. Vein puncture (Venipuncture or Phlebotomy)

2. Finger prick

3. Heel prick

Vein Puncture (Venipuncture or phlebotomy) method:

It is a common method to collect blood samples for diagnostic testing or medical purposes. The vein is punctured by using a sterile needle to withdraw the blood sample. The following steps are followed to withdraw the blood sample by the venipuncture method.

1. Gathering of supplies: The following are gathered: Sterile needle and syringe, vacuum-sealed blood collection tubes, alcohol swabs, tourniquet, cotton balls or gauze pads, adhesive bandages, laboratory sample tube, blood sample tube holder, antiseptic solution, and gloves. The antiseptic solution includes Iodine tincture, Isopropyl alcohol, 70% alcohol, or 5% Savlon solution.

2. Preparation of the patient: Ensure the patient is in a comfortable position then explain the procedure, Locate a suitable arm vein after the patient’s consent. The following two are comfortable positions for a patient.

   Sitting position: Allow the patient a comfortable sitting position in a special chair and put the arm straight on the slanting armrest of the chair.

   Lie down position: Allow the patient comfortable lie down on the back and extend the arm straight. Place a pillow below the arm to support the arm.

3. Hand hygiene: Thoroughly wash your hands using soap and water. Put on gloves to maintain a sterile condition

4. Apply a tourniquet: Apply a tourniquet several inches above the vein puncture site. This restricts the blood flow and makes veins more prominent. The tourniquet should not be applied for more than 1-2 minutes. Applying a tourniquet for a longer duration blocks the blood flow and increases the blood concentration. Remove the tourniquet before the start of blood collection. Sphygmomanometer cough is also used in place of a tourniquet.

5. Puncture Site sanitization: Clean the puncture site using a suitable antiseptic swab. Allow it to air dry. This will make the puncture site free from microorganisms.

6. Vein selection: The median cubital vein in the antecubital fossa (inner elbow area) is most commonly used to withdraw blood samples. Other options are the cephalic vein and basilic vein. These veins are selected because they are close to the skin and easy to assess. The median cubital vein is preferred over the cephalic vein and basilic vein because blood flow in the median cubital vein is faster than the other two veins.

7. Vein puncture: Instruct patient to make a fist. A prominent vein will appear in the antecubital fossa (inner elbow area). Select the proper vein and insert the needle into the vein with a smooth and quick motion. The angle of the needle should be between 15 and 30 degrees.

8. Blood collection: Withdraw the piston of the syringe slowly. Blood will flow into the syringe. Alternately, attach a vacuum-sealed blood collection tube with the needle. The vacuum will draw blood into the tube.

9. Tourniquet removal: Release the tourniquet quickly just after blood starts to flow into the syringe/collection tube.

10. Remove the tube or syringe gently after collection of the required amount of blood. Instruct patient to release fist. Place a cotton ball swab or gauge pad swab on the puncture site and apply gentle pressure. Allow it to remain at the site for 10 to 15 minutes. This will stop bleeding. Alternately, Apply an adhesive bandage on the puncture site.

11. Dispose of sharps and wastes into proper containers.

12. Label the container with have blood sample.

Precautions:

1. Surgery mark or burn mark area on the skin should not be a vein puncture site.

2. Edema: Do not use the site suffering from edema.

3. Haematoma: Do not use the site with blood outside the blood vessel.

4. Fistula or Cannula: Do not use arm have fistula or cannula.

5. Overflow: Do not allow the flow of blood outside the collecting container.

6. Drug: Do not collect blood after intravenous administration of any drug.

7. Blood transfusion: Do not collect blood samples after blood transfusion.

8. Hemolysis: Do not allow hemolysis during blood collection.

Prevention of Haemolysis: The following measures are adopted to prevent hemolysis

1. Add anticoagulants into a syringe or collection tube before collection of the blood sample.

2. Select the proper size of needle and syringe or collection tube.

3. Ensure slow blood flow into a syringe or collection tube.

4. Ensure proper dryness of vein puncture site before insertion of needle.

5. Do not message or squeeze the vein puncture site before blood collection.

6. Do not use a vein puncture site with hematoma.

7. Ensure light fist by the patient.

   Dr Pramila Singh

Finger pricks method

The patient’s middle finger or ringer finger of a non-dominant hand is used to prick the finger for blood sample collection. The following steps are followed in the finger pricks method.

1. Gathering of supplies: The following are gathered: Sterile lancet, lancet device, alcohol swabs, tourniquet, cotton balls or gauze pads, adhesive bandages, blood collection tubes (such as capillary tube, microcuvette, blood collection strip), antiseptic solution, and gloves. The antiseptic solution includes Iodine tincture, Isopropyl alcohol, 70% alcohol, or 5% Savlon solution.

2. Hand hygiene: Thoroughly wash your hands using soap and water. Put on gloves to maintain sterile condition.

3. Lancet device: Load the lancet into the lancet device. Standalone lancet can also be used without the lancet device.

4. Clean the fingertip: Select the proper fingertip and sanitize it using an antiseptic swab or wipe. Rub the fingertip using an antiseptic swab in a circular motion.

5. Position the finger: Access the fingertip; massage the fingertip to flow blood towards the fingertip.

6. Prick the finger: Select a proper site in the slightly off-center of the fingertip to prick. Prick the lancet into the fingertip at 90 degrees angle.

7. Collect blood sample: Gently squeeze the fingertip to increase blood flow. Discard the first drop of the blood because it has tissue fluids. Collect blood in a collection tube by the capillary action.

8. Stop bleeding: Apply gentle pressure on the fingertip by using a cotton ball. Maintain pressure till blood flow stops.

9. Dispose of sharps and other used materials.

10. Label the blood sample container with the required information.

Precautions:

1. Do not select the index finger, it has thick skin,

2. Do not select a little finger, It has a low amount of soft tissues. Pricking may damage the bones and nerves.

3. Do not select the thumb, It is more sensitive.

4. Do not select the center or side of the fingertip of the middle finger or ring finger. These areas have low amounts of soft tissues, pricking may damage nerves and bones.

Heel prick method (Heel stick method or Guthrie test)

This method is used to collect small amounts of blood samples from newborn babies (infants) for medical screening. The following steps are followed in the heel prick method.

1. Gathering of supplies: The following are gathered: Sterile lancet, lancet device, alcohol swabs, tourniquet, cotton balls or gauze pads, adhesive bandages, blood collection tubes (such as a capillary tube, microcuvette, blood collection strip), antiseptic solution, and gloves. The antiseptic solution includes Iodine tincture, Isopropyl alcohol, 70% alcohol, or 5% Savlon solution, and adhesive tapes.

2. Hand hygiene: Thoroughly wash your hands using soap and water. Put on gloves to maintain sterile condition.

3. Lancet device: Load the lancet into the lancet device. Standalone lancet can also be used without a lancet device.

4. Position the baby: Place the baby in a comfortable and secure position. The baby may be in a lying down position on a flat surface or in the lap of caregivers. Ensure accessibility and well support to the baby's foot.

5. Warm heel: Warm the infant heel areas gently. Warm it for 5 minutes at about 40 degrees C by using a warm towel or warm compression. Avoid burning or overheating.

6. Clean the Heel: Clean the heel by using an antiseptic swab. Gently rub the heel with a swab in a circular motion. Allow complete dryness.

7. Prick the heel: Keep the baby's heel firm. Select the proper site and puncture it using a sterile lancet. The depth of the prick will depend upon the age of the baby and the lancet device.

8. Collect blood sample: Squeeze the baby's heel to increase the blood flow. Do not apply much pressure to squeeze. It will promote the flow of tissue fluids with the blood. Discard the first drop of blood because it has tissue fluids. Collect the blood sample.

9. Stop bleeding: Apply gentle pressure on the puncture site using a cotton ball. Maintain pressure to stop bleeding. Apply adhesive tape on the puncture site.

Blood sample transportation for parasite detection

Proper handling and packaging is a must during transportation for accurate test result. The following guidelines are followed during the transportation of the blood sample to a diagnostic laboratory.

1. Collect and label the sample: This ensures accuracy in the identification of the sample. It also prevents the mixing of samples during transportation.

2. Leakproof container: Place the blood sample in a leakproof tight sealed container to avoid leakage during transportation. Place the sample container in a in a zip lock bag.

3. Packaging and cushioning: Place this zip lock bag on a perforated sponge at the bottom of the transportation box. Put another layer of perforated sponge on the zip lock bag inside the transportation box. Place another nonperforated sponge.

4. Protect the sample from temperature changes: Maintain the required temperature during transportation. Required temperatures are frozen temperature (below zero degrees C), refrigerated temperature (2 to 8 degrees C), or normal temperature (18 to 22 degrees C).

5. Documentation: Place the laboratory requisition form or test requisition form inside a zip lock bag with a blood sample.

6. Secure packaging: Put a label or sticker such as “Handle with care”, “Frozen sample”, “Refrigerated sample” etc.,

7. Follow transportation regulations and guidelines.

Blood sample processing for parasite detection

The blood sample processing for parasite detection requires the following steps to isolate and analyze parasites.

1. Verification of sample: The laboratory technician verifies the sample after its receipt. Laboratory technicians shall document and label to ensure accurate identification of samples.

2. Sample preparation: The blood sample undergoes various preparation techniques. These techniques shall depend upon the specific parasite to be detected.

3. Pre-centrifugation: The following steps are carried out after receiving a sample in the laboratory. Then sample undergoes a centrifugation process

4. Addition of additives in the blood sample. Gentle mixing of additives and blood samples by inverting blood sample containers 5 to10 times

5. Proper storage of blood samples at temperatures between 4 degrees and 25 degrees C.

6. Centrifugation: Centrifugation of blood samples is a process of separating red blood cells, white blood cells, platelets, and blood plasma. A chilled blood sample should be preferred for centrifugation for better separation of blood components. Centrifugation of blood samples is carried out at high speed for 10 to 15 minutes. After centrifugation, a blood sample should be analyzed as early as possible.

7. Separation of serum/plasma: Depending upon the type of analysis, Plasma or serum is separated from the blood sample. Plasma is separated from the blood sample by adding an anticoagulant to the blood sample. The serum is separated from the blood sample by allowing blood to clot.

8. Aliquots: The serum or plasma is divided and stored in several smaller containers. These smaller proportions are called aliquots. Each aliquot is a single blood sample. These aliquots are used for multiple tests.

9. Storage and transport: Aliquots and samples are stored under proper conditions bore their analysis. Proper storage maintains the integrity of the aliquot and sample. Proper conditions include exposure to proper lighting and temperature. These proper conditions depend upon the types of analysis and testing to be performed.

Preservation of the blood sample:

Preservation of blood samples ensures the sample is usable and viable for analysis. Following guidelines are followed to preserve the blood sample.

1. Collection: Blood samples are collected by using sterile equipment and proper technique to avoid sample contamination and hemolysis.

2. Anticoagulants: Blood samples should have proper anticoagulants to stop blood clotting. Common anticoagulants are EDTA, heparin, citrate, etc.

3. Containers: Blood samples are stored in sterile plastic or glass containers with air-tight closings.

4. Temperature: The temperature requirement to store blood samples depends upon the test to be performed. These conditions may be frozen temperature (below zero degrees C), refrigerated temperature (2 to 8 degrees C), or normal temperature (18 to 22 degrees C).

5. Time considerations: The gap between blood sample collection and testing/analysis affects the quality of the sample. Blood samples should be processed as quickly as possible. Proper storage and preservation slow down the sample deterioration and microbial growth in the blood sample.

   Author: Dr Pramila Singh