Lecture 2 Flashcards
Why do we still need to look at blood films?
validate numeric data generated by the hematology analyzer
add valuable info that only a trained human can provide
List 6 things that need to be validated in the blood film?
RBC quantity (RBC count, HCT, Hgb) RBC indices (MCV, MCHC, RDW) WBC count WBC differential Platelet count Platelet indices
What 4 things can you add that only a trained human eye can provide?
RBC morphology (clues to cause of anemia)
WBC morphology ( shows whether or not there is inflammatory response or neoplasia)
platelet morphology
infectious diseases
What 4 things are important in a blood film preparation?
- Anticoagulated blood (EDTA tube)
- invert tube at least 8 times before making smear - Fill tube to appropriate line
- Prepare the film asap after collection
- rapidly dry films to prevent air drying artifact (DO NOT heat fix)
2 blood film smear techniques
Push film
Coverslip
What is the name of the stain used for the fixative?
Diff Quik stain
how long do you leave the smear in the fixative?
at least 2 min won’t hurt it to stay longer
What stain is used for detecting reticulocytes and Heinz bodies?
New methylene blue
Can you use tap water to rinse the slide
yes if it is the right pH/ if not need to use distilled
true/ False
You need to wash with water in between stains
False - just let it drip on paper towel in between stains
What results in a refractile artifact or moth eaten appearance?
Water artifact
What does refractile artifact mean?
As you focus up and down on the cell the artifact flashes; in one plane of focus it may appear dark while in another one it may appear bright
What is water artifact often mistaken for?
Red blood cell inclusion ie. parasite
What 3 things can you evaluate from the blood smear grossly?
if the smear was appropriately made
if the animal is anemic
if there is autoagglutination
What part of the blood film is too thick to evaluate?
base
What part of the blood film do you look at to see platelets or parasites ie. big things?
the feathered edge
clumped platelets, large cells, microfilaria, leukocyte inclusions
What part of the blood film is used to evaluate and count RBC and WBC’s?
the “counting area”
What is seen in the feathered edge?
Clumped platelets
large cells
Microfilaria
Leukocyte inclusions
What part of the smear do you evaluate first on low power?
feather edge to check for platelet clumps and microfilaria
IF analyzer says you have a low platelet count (thrombocytopenia) what should you do?
go to the feathered edge to see if there is platelet clumping
what do the RBC’s look like in the feathered edge?
completely flattened and lack central pallor, look like spherocytes. Abnormal shapes are difficult to recognize in this area
What is evaluated in the monolayer on the blood smear?
Estimate platelet number
Estimate leukocyte number and differential count
Morphologic evaluation of all the cells
Data validation
What happens when you place a coverslip on the blood smear?
Big things will appear on the periphery of the coverslip
Where is the monolayer located on the blood smear?
one 10x field behind the feathered edge
Why is the monolayer the optimal area for examination of cells
it dries quickly
cells are spread out and not disrupted
RBC’s are separated with little overlapping
WBC’s are also uniformly distributed
What do you evaluate on the blood smear on low power?
Confirm cell counts
Determine the predominant WBC
Look for big things: platelet clumps, abnormal cells, microfilaria
What WBC cell should be predominate in dogs, cats, and horses?
neutrophils
What WBC will be predominant in birds and reptiles?
lymphocytes
What animal species usually have clumped platelets?
cats
What are clumps of WBC’s referred to as?
Leukergy
What do you evaluate under high power on the blood film?
WBC number and morphology
RBC arrangement, size, shape, color, and inclusions, and validate numeric data
platelet number and morphology
True/ False
It is okay to accept a low platelet count from an automated analyzer w/o confirming it on the blood film
FALSE! - there may be platelet clumping
What is the bare minimum of platelets in dogs and cats?
7-10 per 100x field
How do you estimate platelets counts?
determine average # of platelets per 100x field and multiply by 20,000/microliter
What do large platelets suggest?
increased marrow production of platelets
normal for felids and Cavalier King Charles Spaniels
True/False
the analyzer will still count large platelets
False
How do you estimate the number of leukocytes in the smear?
Take the average # of leukocytes per 100x field after evaluating 10 fields and multiply by 10,000
What 3 things do you do when evaluating platelets on the smear?
Evaluate number of platelets per 100x field (should be at least 7-10)
Estimate platelet count
Check for large platelets
What 3 things do you do when evaluating leukocytes on the smear?
- Estimate leukocyte number per microliter
- Do a differential leukocyte count on 50x or 100x (look at 200 WBC’s and tabulate the type)
- Evaluate leukocyte morphology on 50x and 100x
What do you evaluate neutrophils for?
left shifting and toxicity
What do you evaluate lymphocytes and monocytes for?
Reactivity (will have more cytoplasm)
