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

• A clear separation “valley” must be identified between erythrocyte and platelet peaks

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

Cytogram

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

LEUKOGRAM

• Total and differential leukocyte count

• Assessment of WBC morphologic features.

Neutrophils

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

Reactive Lymphocytes

Erythrogram

• Assessment of red blood cell numbers

• Assessment of

morphologic features

Erythropoesis

Spherocytes

• More spherical than normal disc shaped erythrocytes

• Do not lay flat - appear smaller

• Darker in color • Lack central palor

Autoagglutination

• Immune-induced aggregation of erythrocytes into clusters

Target Cell

• Resemble a bullseye target

• Regenerative anemia • Iron deficiency anemia

Acanthocytes

• Club shaped spicules protruding from erythrocyte

Howell-Jolly Body

• Blue in color • Perfectly round • Small fragments of

nonfunctional nucleus

Heinz Body

• Intracellualr inclusions

• Small, round protrusion on the edge of erythrocytes

Mycoplasma

• Small, blue cocci or rod-like on the edges or across the faces of erythrocytes

Immature neutrophil vs monocyte vs reactive lymphocyte

Immature Erythrocyte vs Lymphocyte

Thrombogram

• Assessment of platelet numbers

• Assessment of platelet size • Assessment of morphologic

features

Macroplatelets

• Large, immature platelet

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.