Haematology

Topic: Different tests done in Routine Haematology

There are many sections in the Department of Haematology. The sections include Routine Haematology, Coagulation, Hb Electrophoresis, bone marrow, flow cytometry, etc.

For the first 4 weeks, I am attached to the Routine Haematology section. There are many tests done in the Routine Haematology lab. Examples of such tests includes ESR, malarial parasite, Hb H inclusion bodies (Thalassemia), reticulocyte count, CBC, differential count, platelet count, body fluid count, etc. In the lab here, ADVIA120 is used for FBC which icludes CBC, differential count, platelet count and reticulocyte count. Reticulocyte count can also be done manually; however, it only applies to neonatal blood.

For this entry, I shall share with all of you more about Erythrocyte Sedimentation Rate (ESR). I will also touch on malarial parasite test, thalassemia and manual retic test.

ESR

For ESR, a circle is indicated on the cap of the EDTA tube during processing at the reception.

Principle

ESR measures the rate of erythrocytes settling in human plasma placed vertically over a time of 1 hour. The value, which is the distance from the bottom of the plasma meniscus to the top of the erythrocyte sediment, is then read off from the pipette in millimeters (mm).

Procedure

1) Check the patient’s particulars on the request form and specimen.
2) Label the pre-filled vial (ESR dilution vial) with the specimen number and record the specimen number into the record book.
3) Use an applicator stick to check for presence of small clots.
4) Mix the blood in the EDTA tube by inverting the tube gently for a minimum of 12 times.
5) Remove the stopper of the vial and pipette 800uL of EDTA blood into the pre-filled vial up to the marking on the vial.
6) Replace the stopper and invert the vial for about 5 to 6 times.
7) Insert the ESR graduated pipette through the pierceable stopper by supporting the pipette and stopper with one hand and use the other hand to hit the pipette down. Then, use both hands to push down the pipette until it touches the bottom of the vial.
8) Allow pipette to stand for exactly 1 hour. Set timer and record the time for reading (1 hour after you set the test) into the record book together with your initials.
9) At 60+/-1 min, record the distance, in mm.
10) Record the numerical values into the record book and enter result in the Meditech system (LIS) with initials. If results are greater than 140 mm/hr, it is reported as >140 mm/hr.


Range: Male (1 – 10 mm/hr)
Female, up to age 50 (3-15 mm/hr)
age 51 and above (3-20 mm/hr)


Factors affecting ESR:
- Erythrocyte-plasma ratio
- Bore of the tube
- Hct
- Verticality of sedimentation tube
- Dilution of blood sample.
- ESR also depends on the ability of erythrocytes to form rouleaux. If there is an increased in the concentration of plasma proteins (mainly fibrinogen), erythrocytes are able to form rouleaux thus there will be an increase in ESR.


Malarial Parasite

To test for malarial parasites:
Prepare 2 thick and 1 thin blood films.

Thick films are prepared by using 2 applicator sticks to drop the blood onto the slide and spread to the size of a 10cent coin. It is best to lyse the RBCs so that the malarial parasites can leak out from the RBCs if there is any. The thick films are then air-dried at room temperature before staining it with diluted Giemsa stain for about 15mins. Diluted Giemsa stain is made up of 9 parts of pH7.2 buffer and 1 part of Giemsa stain. After 15mins, the slides are then rinsed with pH7.2 buffer.

For preparation of thin films, it is the same as doing the normal blood smear using the spreader. The thin films are then stained with Leishman’s or Wright’s stain for 7mins or placed into the autostainer.

NOTE: Thick films should not be dried in 37 degrees incubator or exposed to heat.

Thalassemia

Add the same amount of stain (1% brilliant cresyl blue) and blood into the test tube. Incubate in the water bath for 1 hour. Use paraffin to cover the tube to prevent evaporation. After 1 hour, do a blood smear.


Manual Retic

Manual retic is done only for neonatal blood or when ADVIA120 (the machine we are using) shows an asterisk under the value for retic count.

It is done in almost the same way as thalassemia. The same amount of stain (1% brilliant cresyl blue) and blood into the test tube. Incubate in the water bath for 15 mins. After 15 mins, a blood smear is done.

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All the smears/blood films for FBC, malarial parasite, thalassemia and retic done are sent to the screener to be examined under the microscope.

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POSTED BY:
Malerie
TG 02