Hematopoietic disorders and classification of anemia Flashcards
Function of RBC
Transport and protect hemoglobin
Transport O2 from the lungs to the tissues and CO2 from the tissues to the lungs to be expired
In a normal animal, the daily production of RBCs equals the daily loss due to the destruction of aged cells
Anemia is and can be due to
Anemia is when the oxygen-carrying capacity of erythrocytes is reduced. This may be due to:
-Reduced numbers of circulating RBCs
-Reduced PCV
-Reduced hemoglobin concentration
-If RBC production is decreased or RBCs are being lost
It is only a symptom of another disease process, there is always an underlying cause
Classification of anemia
There are a number of ways in which anemia can be classified:
By bone marrow response
By red blood cell size and hemoglobin concentration
MCV and MCHC
By the underlying etiology
Classification based on bone marrow response and RBC parameters will help to identify the cause of the anemia
Tests used to determine the cause of anemia
Reticulocyte count
Erythrocyte indices
PCV
RBC morphology
Plasma color and turbidity
Total plasma protein concentration
Specialty lab results used for diagnosis of anemia
Coombs test
Serum iron levels
Fecal examination for GI blood loss
Antigen or antibody tests for specific diseases
FeLV, FIV, EIA, feline hemotropic mycoplasmosis, blood borne parasites
Biochemical assays
Bone marrow evaluation
How do you use the bone marrow response to classify anemia
The most clinically applicable classification system
Classifies the anemia as either regenerative or nonregenerative
The bone marrow’s response to anemia should be to increase RBC production and to release immature RBCs
Assessment of the bone marrow response is based on the number of immature RBCs present in circulation
Polychromatic RBCs or nucleated RBCs
Determined by performing a reticulocyte count
Regenerative anemia is
The presence of reticulocytes means that the bone marrow is responding, therefore there is a regenerative response
Anemia is likely due to either hemorrhage or hemolysis
It takes about 4–7 days for immature RBCs to appear in peripheral blood after blood loss or destruction
The exception is in horses
A patient is considered to have an adequate bone marrow response when their reticulocyte count is equal to or greater than the expected value for the patient’s PCV
Regenerative anemia in horses
Horses do not release polychromatic cells from the bone marrow, therefore a bone marrow aspirate is necessary to evaluate reticulocyte numbers
They will release macrocytic, normochromic cells
Reticulocyte counts of greater than 5% from the bone marrow aspirate indicates a regenerative anemia
Nen-regenerative anemia
A nonregenerative anemia is defined as a low RBC mass with no evidence of a bone marrow response in the peripheral blood
No polychromasia or reticulocytes
RBCs are normochromic
A bone marrow aspirate is indicated after endocrine and metabolic causes of a nonregenerative anemia have been ruled out
Attributed to bone marrow dysfunction, or the inability of the bone marrow to produce RBCs
Further classified based on whether granulopoiesis and thrombopoiesis are also involved in the bone marrow dysfunction
Some causes of nonregnerative anemia are
Iron deficiency
Ehrlichiosis
Drug toxicity
Histoplasmosis
Hypothyroidism
Renal insufficiency
Chronic disease
Chronic infection
Chronic liver disease
Nutritional deficiencies or intestinal malabsorption
Toxins-lead
Hormonal imbalances
Classification by RBC Size and Hemoglobin Concentration
Classifies anemia as either normocytic, macrocytic, or microcytic
Uses MCV and MCHC
Macrocytic anemia
-Usually seen with regenerative anemia
Microcytic anemia
-Almost always the result of an iron deficiency
Animals with a normocytic anemia usually have a nonregenerative anemia or a preregenerative anemia
-Preregenerative- it is too early in the disease course to see a bone marrow response
Anemias can also be classified as either hypochromic or normochromic
-A hyperchromic state is not possible
Polychromatic RBCs contain less hemoglobin than a mature RBC, therefore they are technically considered hypochromic (though they don’t appear this way)
-They appear to be hyperchromic due to the staining of the nuclear remnants
Hypochromic, microcytic anemia is almost always due to iron deficiencies
-Low MCV and MCHC
All other anemias are normochromic
Classification of etiology of anemia
Hemolytic
Hemorrhagic
Iron deficiency
Production disorders
Or combinations of the above
Hemolytic anemia is and due to
Due to erythrocyte destruction
Theses animals usually develop a regenerative anaemia
During the pre regenerative phase they will have a normocytic, normochromic anemia
RBC destruction may be intravascular or extravascular
It is caused by immune-mediated destruction, erythrocyte parasites, bacterial and viral agents, and toxin exposure
Clinical signs of hemolytic anemia
Lethargy
Splenomegaly
Fever
Icterus
Pale mucous membranes
Dyspnea
Tachycardia
Systolic heart murmur
Syncope
Laboratory findings with hemolytic anemia
Decreased PCV
Decreased red blood cell count
Decreased hemoglobin concentration
Inflammatory leukogram
Hemoglobinemia, hemoglobinuria, hyperbilirubinemia & bilirubinuria
Positive Coomb’s Test
With immune mediated forms of hemolytic anemia
Immune mediated hemolytic anemia is and due to
Due to increased red cell destruction
Occurs as a result of antibodies directed against the RBC itself or immune complexes that attach to the RBC
It will produce a marked regenerative anemia
This is the most common cause of hemolytic anemia in dogs
Common in Cocker Spaniels, Poodles & Collies
Has also been seen in horses, cattle and cats
What does a blood smear with immune mediate hemolytic anemia look like
Spherocytes**
Agglutination
+/- Thrombocytopenia
Increased polychromasia
Neonatal isoerythrolysis is and due to
A form of IMHA
Due to antibodies from the dam against the neonate’s RBCs
In most species, there must be either previous exposure to blood products or a previous pregnancy
Mismatched blood transfusions cause a similar reaction
Most common in horses & mules, also seen in kittens
Neonates are healthy when born and become weak, lethargic, pale, anemic, icteric and dyspneic within 12 hours to 4 days post partum
Lab findings for neonatal isoerytholysis
Coomb’s test positive
Dam can be tested 2 weeks prior to parturition to predict the likelihood of neonatal isoerythrolysis
Equine–mares most frequently develop antibodies to blood types Aa and Qa
Feline–type A or AB kittens born to type B queens
Erythrocyte parasites common in sk are
Mycoplasma haemofelis
Anaplasma
Babesia
Ehrlichia
Common infectious agents that cause anemia
Most of these pathogens can cause at least two types of anemia
FeLV
Leptospira
EIA virus
Heinz body anemia is and caused by
Oxidative damage to the RBC
Cats are more susceptible than other domestic species
Can be due to medications, chemicals, plants, inherited enzyme deficiencies and nutritional deficiencies or toxicities