Understanding the hemogram Flashcards
Why is it better to do a blood smear with fresh blood rather than with stored EDTA anti-coagulated blood cells
EDTA anti-coagulated blood cells could suffer artifacts
Why is it important to always make a blood smear along with a hemogram
Red and white blood cell counts may be within reference ranges, but cell morphology may indicate the presence of a number of significant changes, for example, toxic neutrophils, circulating blasts, abnormal RBC morphology or RBC parasites
Give a definition of Packed Cell Volume (hematoocrit)
This value describes the proportion or percentage of the blood volume taken up by the RBCs
Give a simple interpretation of elevations and diminution in the PCV
Elevations in the PCV may indicate:
- An absolute increase in red cell mass (polycythemia or erythrocytosis
- A relative increase due to hemoconcentration (dehydration)
Diminutions in the PCV (anemia) may be due to:
- Increased red blood cell loss (hemolysis or blood loss)
- Decreased production by the bone marrow
What is the signification of Hemoglobin value in a blood analysis
It is measured in g/dL
The hemoglobin concentration is the most reliable indicator of the blood’s oxygen carrying capacity
This value may be artifactually elevated in the presence of lipemia, and large numbers of leukocytes or Heinz bodies
What is the Red Cell Count
This value is given as an absolute number of cells per liter of blood and is measured using an automated cell counter
What are the red cell indices useful for
The red cell indices are used to help classify anemia (regenerative versus non-regenerative)
They may also give some clues as to the underlying etiology
What is the Mean corpuscular volume and why is it useful
This measures the average size of the red blood cells (MCV = PCV/RCC), that is “volume per cell”
This value is used to classify the erythron as “microcitic”, “normocytic”, or “macrocytic”
Give some causes of micorcytosis
Microcytosis (with hypochromia) is typically observed in animals with iron deficiency anemia
- It may also been seen in animals with portosystemic shunts, as they have altered iron metabolism
Give some causes of macrocytosis
Macrocytosis is generally observed in assoication with regenerative anemia, as reticulocytes are larger than mature RBCs
Macrocytosis can also be observed in conjunction with non-regenerative anemia associated with myeloproliferative disorders, myelodysplasia or in cats infected with FeLV
It is also seen with hypocobalaminemia
What is the “red cell distribution width”
The “red cell distribution width” (RDW) is available on some analyzers and estimates the degree of anisocytosis in the blood
A high RDW can indicate the presence of microcytosis and/or macrocytosis
- But it may be artifactually affected by the overlap in size of feline RBCs and platelets
What is the signification of “Mean Corpuscular Hemoglobin Concentration)
Measuring the amount of hemoglobin in the red blood cells helps to classify anemia as:
- “normochromic” (normal MCHC; these are typically non-regenerative)
- “hypochromic”: may be seen if there is regeneration (typically with macrocytosis) or iron deficiency (with microcytosis)
What is the signification of an increased MCHC
A red blood cell cannot physically carry more hemoglobin than normal
An increased MCHC is usually reflective of hemolysis
What is the signification of reticulocyte count and how reticulocytes appear on a blood smear
The presence of reticulocytes indicates a regenerative response to anemia
Reticulocytes can be suspected on a blood smear in an animal with regenerative anemia because there will be polychromatophily and anisocytosis
They are better visualized with new methylen blue staining
What is the signification of the observation of nucleated red blood cells (nRBC)
Increased numbers of nucleated RBCs (also known as rubricytosis) may occasionally be observed in animals with:
- a regenerative response
- bone marrow disease
- splenic disorders (reduced removal of nRBCs from circulation)
- lead toxicity (in this case basophilic stippling of RBCs caused by aggregation of ribosomes may also be observed
Occasional nRBCs can be normal in cats
What is the difference between rouleaux and agglutination of RBCs? How can you differentiate the two conditions
Clumping of red cells is commonly seen on feline blood smears
- if RBCs line up in a stack this is termed “rouleaux”
- if RBCs appear as bunches of grapes this is termed agglutination
Quite commonly observed in the cat, rouleaux is not normally associated with a specific pathologic process, but may be more proeminent when there are high levels of plasma proteins
Rouleaux can be differentiated from agglutination by mixing 1 drop of blood with 1 drop of saline on a slide
- If RBC clumping persists, this is more likely to be true agglutination
Explain why spherocytes are not commonly observed in cats
Feline RBCs are round (not discoid), small and lack the central pallor of canine RBCs
Spherocytes, which are a marker for immune mediated hemolytic anemia in dogs are not routinely observed in cats
What is the meaning of “anisocytosis”
Anisocytosis means a variation in RBC size
Usually this is because of the presence of reticulocytes, and indicates a regenerative response
What is the definition for “poikilocytosis”
Poikilocytes are RBCs with abnormal shapes
Different abnormalities are seen with different disease processes
Give a definition of “Echinocytes” and give two artifactual reasons for their presence
Echinocytes are crenated RBCs
Echinocytes can be seen in blood that has been anticoagulated with too much EDTA, or when blood has been stored too long before the blood smear was made
What are schisocytes
Schisocytes are RBC fragments caused by mechanical trauma to RBCs in vivo
What are acanthocytes
Acanthocytes have irregular finger-like projections of their membrane, which is caused by alterations in the amount of cholesterol and phospholipids
These cells may be associated with liver or kidney disease in cats
What are target cells
They have an area of central pallor because they have excessive amounts of membrane compared to their cytoplasmic volume
They are often associated with liver disease
What are eccentrocytes
Eccentrocytes are cells where the hemoglobin gathers to one side of the cell, producing a cell that is 1/2 stained and 1/2 clear
This is caused by oxidative injury to the cell membrane
What are keratocytes (=helmet cells)
Keratocytes have little horn-like projections
These RBCs are thought to form when the cell is damaged when it encounters fibrin within the blood vessels
What are dacrocytes
Dacrocytes are tear drop shaped RBCs that are seen with bone marrow disorders, such as myelophtisis
What is the cause of Heinz bodies formation? What is their signification
Heinz bodies are the result of oxidative damage to hemoglobin and are more readily seen with vital stains such as new methylene blue
Low numbers are regularly seen in cats due to the non-sinusoidal nature of the feline spleen, which is not as efficient at clearing these RBCs from circulation
What are Howell-Jolly bodies
Howell-Jolly bodies are small dark remnants of nuclear material seen with Diff-Quick staining
Increased numbers can be seen in regenerative anemia
It is normal for cats to have Howell-Jolly bodies in up to 1% of RBCs
What is basophilic stippling and what is it signification
Basophilic stippling is the appearance of multiple dark blue dots within RBCs
- These granules are precipitated ribosomal RNA
Basophilic sqtippling is sometimes seen within polychromatophils as part of a regenerative response
If basophilic stippling is observed in mature RBCs with no accompanying anemia, lead toxicity should be suspected
- Lead toxicity causes an acquired deficiency of the enzyme 5-nucleotidase, which prevents breakdown of RNA
- Often there is a concurrent increase in the numbers of nucleated RBCs in animals with lead toxicity
