Flashcards for Lab Prep
For a blood smear, how much blood should be added to the slide?
6 μl
What end should the frosting be at?
Right
In a good blood smear, what are you looking for?
Nice smooth spreading on the slide, margin of white blood cells around the periphery
What angle should the blood be spread at?
30°
How full should the microhaematocrit tube be to calculate PCV?
3/4 full
How many times should the microhaematocrit tube be inserted into the wax and why?
Twice to ensure a good seal
Why should the finger always be on the top of the microhaematocrit tube?
To prevent blood from leaking
How is the packed cell volume (PCV) calculated?
(Distance red blood cells travelled / distance blood sample travelled) x 100
What dilution of blood is used for the absolute white blood cell count?
1:20 (50 μl:950 μl)
What solution is used to dilute the blood for the absolute white blood cell count?
Erythrocyte lysis buffer A
After mixing, how long should the white blood cell count solution have to stand?
2 minutes
What dilution of blood is used for the absolute red blood cell count?
1:200 (5 μl:995 μl)
What solution is used to dilute the blood for the absolute red blood cell count?
PBS
After mixing, how long should the red blood cell count solution have to stand?
None (instantly)
What dilution of blood is used for the absolute platelet count?
1:20 (50 μl:950 μl)
What solution is used to dilute the blood for the platelet cell count?
Erythrocyte lysis buffer B
After mixing, how long should the platelet count solution have to stand?
At least 10 minutes
How should the samples be loaded into the haemocytometer?
Top down, in the gap between the coverslip and the grid
How much of the sample should be loaded into each chamber of the haemocytometer?
10 μl
What setting on the microscope makes it the easiest to count cells?
Phase contrast
How can red blood cells and platelets be visualised on the haemocytometer?
Using the small central grid
How can white blood cells be visualised on the haemocytometer?
One of the four large corner grids
What cells should be counted?
To save counting some twice, only those cells that fall within each square or lie on two of the four border lines of each should be counted
What is the formula to calculate the viable cell density?
Average corner count x 10⁴ x Dilution factor
What is the formula to calculate the percentage viability?
Total viable cell count / Total cell count x 100
How to recognise a neutrophil
~62-70% of total WBC count, 10-12 μm in diameter, mulitlobed nucleus with fine/faintstained cytoplasmic granules
How to recognise an eosinophil
~2.3% of total WBC count, 10-12 μm in diameter with a bi-lobed nucleus, cytoplasmic granules are heavily stained with eosin
How to recognise a basophil
~0.4% of total WBC count, 12-15 μm in diameter with bi/tri-lobed nucleus, cytoplasmic granules are large heavy blue stained
How to recognise a lymphocyte
30% of total WBC count, small = 7-8 μm and large + 12-15 μm in diameter with darkly stained eccentric nucleus with small amount of cytoplasm
How to recognise a monocyte
~5.3% of total WBC count, 8-10 μm in diameter with a kidney shaped nucleus, granular with abundant cytoplasm
What is the average number of red blood cells per μl?
4-6 x10⁶
What is the average number of white blood cells per μl?
4-11 x 10³
What is the average number of lymphocytes per μl?
1.3-4.0 x 10³
What is the average number of neutrophils per μl?
2-8 x 10³
What is the average number of monocytes per μl?
0.2-0.8 x 10³
What is the average number of platelets per μl?
1-4 x 10⁵
What is a normal person’s international normalised ratio (INR) range?
0.9-1.3
What is a warfarin patient’s international normalised ratio (INR) range?
2-3
What is the reference range for PT of normal plasma?
12-15 seconds
Method for prothrombin (PT) test
- Add to 100 μl plasma to 200 μl of PT reagent. Start the stopwatch
- Incubate with gentle agitation
- The endpoint (given in seconds) is where the clot forms
- Repeat the assay and calculate the mean
What is the reference range for APTT of normal plasma?
25-45 seconds
Method for activated partial thromboplastin time (APTT) test
- Mix 100 μl plasma sample with 100 μl APTT reagent in a 12x77 mm borosilicate glass tube & incubate for 3 minutes
- Add 100 μl CaCl₂ solution & simultaneously start stopwatch
- Leave tube for about 20 seconds then gently tilt the tube to observe clotting
- The endpoint (given in seconds) is when the clot forms
- Repeat the assay and calculate the mean
