Download What your hematology instrument isn`t telling you

What your hematology instrument isn’t telling you
What your analyzer will not (or may not) tell you.
• Abnormal leukocyte morphology or toxic change
• Abnormal erythrocyte morphology
• Immature cells
• Platelet clumps
• Intra- or extracellular infectious agents
• Inclusions
• Abnormal proteins
• Abnormal platelet morphology
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What your blood smear can tell you.
Confirm leukocyte counts + differentials
Confirm the presence of nRBCs, platelet
clumps, blasts, agglutination, rouleaux
Assess morphology lf erythrocytes,
leukocytes, and platelets
Identify intra- or extracellular infectious
agents
Identify inclusions, e.g. Heinz bodies
Blood smear preparation – the first part of blood smear review
Preparing a high quality, well-stained blood smear is one of the most important aspects of the CBC.
1. Plan to make the blood smear(s) as soon as possible after blood collection.
2. Draw up a small amount of blood using a microhematocrit tube and immediately place a SMALL drop
of blood on one end of the slide.
3. Use a clean (spreader) slide to drag this drop of blood to make a smear.
4. The spreader slide is backed up into the drop of blood and then shoved forward, dragging a film of
blood with it, as the direction arrow shows in the figure below.
5. The slide with the drop of blood on it should be held firmly on the table during the spreading. The
spreader slide should be shoved forward in a firm manner to avoid chatter (skipping).
6. Increasing the angle of the spreader slide results in thicker, shorter smears (i.e. anemic patient).
7. Decreasing the angle results in thinner, longer smears (i.e. in patients with a high PCV/polycythemia).
8. Dry the smear quickly (i.e. hair dryer, heat block, etc)
Note: A correctly made smear will have a colorful sheen when help up to the light, reflective of a
monolayer of cells. This sheen is visible in the unstained, but not stained smear.
9. Stain the blood smear
• Keep the stain clean & refresh the methanol (step 1) often.
• Dip the smear into each of the 3 Diff Quick containers 15-20 times.
• Leave 1 or 2 smears unstained in case review by a pathologist is necessary.
10. Air dry slide completely.
PVMA - November 2016 - Nicole Weinstein, DVM, DACVP – Penn Vet Clinical Pathology
General comments
Low magnification
(4x or 10x)
Low magnification
(10x)
in monolayer
High
magnification
(40x or 100x)
in monolayer
Blood smear review procedure
• Remain in the monolayer (except when examining feathered edge)
• No oil for 40x – 40x only works with a coverslipped slide &
o To use 40x: slide + drop of oil + coverslip for blood smears
• Oil needed for 100x
• Examine feathered edge for:
o Platelet clumps
o Microfilaria, large atypical cells, etc.
o Lots of leukocytes at edge—may decrease WBC slide assessment
§ Make slide faster to prevent this
• Determine leukocyte density (assuming normal distribution)
o ‘Normal’ is 18-52/10x field (dog)
o Can estimate also using formula & smear with normal distribution of leukocytes
§ Average # WBC/10 fields x objective2
§ Example: Average # WBC/10 fields = 10; Objective = 40x
• 10 x 40 x 40 = 16,000/ul
• Make sure ‘leukocytes’ aren’t nRBCs if counting on lower magnification
RBC:
o Determine RBC density with spun PCV
o If anemic, is there evidence of regeneration (polychromasia)?
o Can confirm with NMB slide.
o Increased nRBCs?
o Appropriate (concurrent anemia & regeneration) or inappropriate?
o Hypochromasia – present?
o Poikilocytosis
o Acanthocytes, schistocytes, keratocytes, target cells, eccentrocytes, spherocytes,
microcytes, echinocytes, etc.
o Heinz bodies (especially if anemic)
o @5-10% small HBs in cat can be normal
o Confirm with new methylene blue or brilliant cresyl blue slide
§ 1 drop of blood + either vital stain + 15 minutes, then make slide
o Hemic parasites (especially if anemic) – need 100x
o Cats: Mycoplasma sp., Cytauxzoan sp.
o Dogs: Babesia sp., Mycoplasma sp.
o Beware of water artifact, stain precipitates, & Howell Jolly bodies (mimic
parasites)
o Other inclusions:
o Distemper inclusions (in RBCs or WBCs)
o Granules or vacuoles in WBCs (storage diseases)
WBC
o In monolayer, determine WBC differential & include:
o Neutrophils, bands (+ any immature), lymphocytes, monocytes, eosinophils,
basophils
o Numbers of nRBCs (per 100 WBC is standard)
o Atypical or unclassified cells/blasts, reactive lymphocytes
o Inclusions: Rickettsial morulae, Histoplasma, distemper inclusions, granules, vacuoles, iron
PLATELETS
o Always review slide on 4x or 10x for clumps. If clumps present, then estimate is minimum
o On 100x, platelet estimate
o 1 platelet = 15,000/ul (15,000-20,000/ul)
o Normal (dogs) = 15 – 25/100x field
o Giant platelets may be present (some breed abnormalities)
PVMA - November 2016 - Nicole Weinstein, DVM, DACVP – Penn Vet Clinical Pathology