incorporating differentials into every complete blood … · incorporating differentials into every...
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Incorporating Differentials Into Every Complete Blood Count
Paige Flowers, LVT Dogwood Veterinary Internal Medicine
Complete Blood Count
Diagnostic performed to evaluate the quantity and morphology of the cellular components of blood. Automated cell count PCV/TS Manual Differential
Sample Collection and Handling
• Fill EDTA tubes until vacuum flow stops – Ensures appropriate blood volume to
anticoagulant ratio – Prevents overfilling
• If not analyzed within 2-3 hours, EDTA blood should be refrigerated – Minimal changes in refrigerator for up to 24 hours
Automated Cell Counters
Impedance Principle {aka: The Coultier Principle} Quantifies cells Identifies cells by size and density
Automated Cell Counters
• Platelet-erythrocyte histograms
– used to evaluate for mechanical errors – Overlap in the size of platelets and erythrocytes indicates the
machine cannot differentiate between the two
Automated Cell Counters
• Laser Light Scatter – Laser detection system in a flow cytometer to
measure size and internal complexity of cells – Able to make distinctions that are undetectable
using impedance
PCV vs HCT – HCT
• (RBCs x MCV) 10 – PCV
• Centrifugation of blood to pack erythrocytes and determine a packed cell volume
The variation between HCT and PCV should not exceed 5%
• Suggests technical error
The Differential
• Complements automated cell counters • Often provides diagnostic information that an
automated cell counter cannot – Even without an automated cell count
The Blood Smear
• Prepare immediately • Monolayer
– Provides optimal morphologic detail
– Good distribution – Stains well – Cells lay flat
The Blood Smear
• Only cells with sufficient morphologic detail should be included in the differential cell count – A large percentage could be
cause for concern
Neutrophils
• Toxic neutrophils – Indicates more
severe disease, a worse prognosis and longer hospital stays
– Moderate to severe toxic changes can cause signs such as fever, vomiting, diarrhea or shock like symptoms
Eosinophils
• Orange - pink granules
• Shorter and less segmented than neutrophil nuclei • Cytoplasm, if visible, is pale blue.
Basophils
• Canine • ribbon-like nucleus • gray-lavender hue
• Feline
• small, slightly oval granules • pale lavender
Monocytes
• Variable in size and appearance
• Usually largest leukocyte
• Nucleus can be round to kidney-shaped to pseudo-lobulated
Lymphocytes
• small (mature) cells
• round nuclei
• smooth, dense chromatin
• small rim of light blue cytoplasm
Lymphocyte sizes
Lymphocyte size Nucleus size relative to neutrophil Small Nucleus of lymphocyte can fit
inside a neutrophil Intermediate Nucleus of lymphocyte is the
same size as a neutrophil Large Neutrophil can fit inside the
nucleus
Spherocytes
• More spherical than normal disc shaped erythrocytes
• Do not lay flat - appear smaller
• Darker in color • Lack central palor
Thrombogram
• Assessment of platelet numbers
• Assessment of platelet size • Assessment of morphologic
features
Willard, DVM, MS, DACVIM, Michael, and Harold Tvedten, DVM, PhD, DACVP, DACVCP. "The Complete Blood Count, Bone Marrow Examination and Blood Banking." Small Animal Clinical Diagnosis by Laboratory Methods. Fifth ed. St. Louis: Elsevier, 2012. 12-29. Print. "Hemogram Basics." EClinpath. Cornell University College of Veterinary Medicine, 2013. Web. 16 Oct. 2015.