Lecture 2 - Blood film evaluation Flashcards
What should you do to validate the data given by a hematology analyzer?
look at blood film, also gives info that analyzer can’t pick up
what are 4 things that a machine can’t pick up that a trained person can when evaluating blood films
- RBC morphology: clues to anemia cause
- WBC morphology: +/- inflammatory or neoplastic dz
- platelet morphology
- infectious dz/parasite
what tube is preferred for making blood films
EDTA (purple top)
note: green top can be used but causes cells to appear blue/green
ideally a blood films should be prepared…
make ASAP after collection (push film or cover slip method)
gently invert the tube 8-10 times
do not heat fix but rapidly dry to prevent artifacts
staining blood film with diff-quik stain should let it sit in fixative for __
2 minutes
3 romanowsky type stains and what is the most common one
- diff-quik (most common)
- wright stain
- wright-giemsa stain
__ is used to stain reticulocytes (anemia) and heinz bodies (oxidative damage)
new methylene blue
__ is used to stain iron for BM samples
prussian blue stain
using __ will prevent pH changes/funky looking slides
distilled water, but tap water is okay to use if it’s the right pH
__ is a refractile artifact that can result in moth-eaten appearance and is normally due to poorly maintained quik stains
water artifact (water in fixative)
__ is often mistaken for RBC inclusions (parasites like Mycoplasma)
water refractile artifact
__ means that when focused up and down on cell the artifact “flashes” in one plane of focus, appearing dark in one while bright in another
refractile
After prep and staining the film what should be done
examine grossly for quality of smear, anemia, autoagglutination
After examining the slide grossly what is done
evaluate on low (10-20x) then high/oil (50-100x) power
big clumps of platelets, large cells, microfilaria and leukocyte inclusions can be seen in what part of the peripheral blood film
feathered edge (rainbow region)
where should you count on peripheral blood film
monolayer, middle between the feathered edge and the base where the RBC are spread out and WBC are easy to see
__ is the first part of the blood film examined on low power
feathered edge (look for platelet clumps and microfilaria) do not use for counting!
__ in the feathered edge are excessively spread and appear larger than they should, a lot of cells are also smudged here
leukocytes
RBC in the feathered edge are completely flattened and lack a central pallor which mimic __, abnormal shapes are hard to ddx in this area
spherocytes
what 4 things do you look for in the monolayer
- platelet estimate
- WBC estimate and differential
- morphologic eval of ALL cells
- data validation
The coverslip method makes one big __ layer
monolayer
in the __ layer about on 10x field behind the feathered edge the RBC are spearated or barely touching/not overlapping and the WBC are uniformly distributed
monolayer
First step to systematic blood film eval is
view on low power in a good area to confirm cell counts, assess dom WBC, and look for “big” things
leukocyte clumping is called __, automated WBC count falsely decreased by this
leukergy
most machines won’t report __ such as the “big blue uglies”
atypical WBC (BBU are immature lymphocytes)
On high power look for WBC and Platelet #/morphology and what 5 RBC things (only a human can do these things!!!)
- arrangement
- size
- shape
- color
- inclusions
Normal min amount of platelets/100x field in dogs and cats
7-10
to estimate platelet count
multiply the average # of platelets for 10 fields then multiply by 20,000/mcL
large platelets suggest __ but can be normal for
BM production
normal: felids and cavalier king charles spaniels (macrothrombocytopenia is normal for these)
how many WBC should be counted on high power for a WBC differential
200
what 4 morphological features of WBC are looked for on high power (only a human can do these!!!!)
- neutrophil - left shift or toxicity
- lymphocyte and monocyte reactivity
- parasites
- atypical or neoplastic cells
to estimate WBC
on 100x: average # (at least 10 fields) x 10,000 = WBC/mcL
if using an objective other than 100x how do you estimate WBC
average #wbc x Square of the objective power used to do the count. (for 100x = 10,000)
