5. Preparing and evaluating blood smears Flashcards
What can you see with a properly made blood smear
A differential WBC cound can be done - will be able to calculate the relative # of each type of WBC
RBC estimation and morphology can be evaluated
platelet estimation and morphology can be evaluated
identify blood parasites or other organisms
What are the 2 methods of preparing blood smears
- wedge technique
- coverslip technique
How are blood smears made using the coverslip technique?
drop of blood placed on a coverslip
2nd coverslip placed diagonally on top of the first
once the area btw the coverslips is almost completely filled with blood, separate the coverslips in a smooth motion
allow to air dry
What are some things to worry about when doing the wedge technique method?
most commonly used technique
good quality smears req for accurate
be sure your slides are clean and dry
don’t touch flat surfaces of slides with fingers
use one drop of fresh whole blood if possible, if not use EDTA as anticoagulant - mix sample well before drawing up sample
How do you make a wedge blood smear
label appropriately w/ name + date on frosted edge
Select a second slide - ensure it does not have chips or burrs on the short edge of slide
drop blood near frosted end of slide
Hold slide @ 30-45 angle, index/middle finger on frosted end of slide and pull short end of spreader slide into drop of blood, once blood has spread approx 2/3 -3/4 width of slide, push slide across bottom slide.
Once you’ve made your blood smear, what are you looking for, what do you want to have? What are post-smear preparation
want flame/thumb shaped smear of good size that is neither too thin or too thick
want to have a large monolayer (one cell layer thick)
gently wave the smear in the air to dry it rapidly to prevent artifacts from forming
if the smear isn’t the correct shape, ti will alter cell distribution and therefore cell counts
What are some problems that might arise when making a blood smear?
artefacts will develop if slide dries too slowly
if smear is thin- the angle may have been <30 degrees, it was spread too quickly or patient is anemic
If smear too thick - angle >45 degrees, moo much blood was used or the patient is hemoconcentrated - WBCs will appear small and dark, cells will be overlapping and difficult to evaluate, monolayer will be thin
if push too slow, the segmented WBC’s and monocytes will be concentrated at feathered edge and will distort cells
Why is staining the slide importan?
to differentiate the diff WBC types and aid in the detection of any abnormalities that may be present
When do we stain the slide
once it is completely dried
What stain is used?
Any romanowsky stain can be used - includes writght’s stain, giemsa stain or modified wright’s stain
available in a one-step or three-step process
diff-quick is the most common - this is what we will use in the lab
WHat do we need to keep in mind once the slide is stained
wear gloves, last step is to rise with distilled water
slide must be dry b4 evaluation
eval slide grossly b4 looking at it with the microscope, allow to determine if slide is prepared properly
look @ size and shape of the blood smear
eval the monolayer
look for evidence of air bubbles, streaks or stain precipitate within the smear, eval the intensity of staining
How is staining with modified wright’s stains done?
fast, easy, consistent
dip dry blood smear in solution 1 - 5 1 second dips
repeat for solutions 2-3
rinse in distilled water
let slide dry with the feathered edge up
microscopic examination of the slide when it is completely dry
