Erythrocyte evaluation Flashcards
Haematopoiesis: Cell lines produced from pluripotent stem cells
- 2 major lines of division: - Lymphopoiesis - Myelopoiesis
Production: 6 specific requirements
- Stem cells
- Space in the marrow for cell development (minimal fat/fibrous tissue)
- Growth factors (e.g. erythropoietin produced by the kidney)
- Iron (synthesis of haemoglobin)
- Cholesterol/lipids (formation of cell membranes)
- Enzyme pathways for construction/maintenance of cells (e.g. pathway to allow RBCs to utilise glucose)
Red cell lifespan
- Dog
- Cat
- Cow
- Horse
- 110 day
- 70 days
- 160 days
- 145 days
Note: Horse will take longer to show signs of anaemia compared to cat
Aged RBCs:
- Altered enzymes/cell membrane
- Cell membrane more rigid
- Difficult to deform
- Unable to pass through blood vessel - Aged RBCs enter the spleen and liver
- Changes allow detection by macrophages
- Undergo macrophage phagocytosis
RBC components recycled:
Extravascular haemolysis:
- Spleen, liver, lymph node and marrow
- Hb is broken down
- Fe is stored in the liver and recycled
- Globin is added to the AA pool in the liver, spleen etc.
- Bilirubin is conjugated/excreted into the faeces
Intravascular haemolysis:
- Small number of RBCs lose in the vascular system
- Free Hb from these produces:
- Haptoglobin
- Methaemoglobin
- Haemaglobinuria
Red blood cell production sites:
Foetus: Liver & spleen
Neonate/adult: Bone marrow (long bones - femur/humerus/pelvis/ribs)
Adults: Liver & spleen maintain erythropoietic capacity
- Especially with increased demand
- Known as extramedullary haematopoiesis
Anaemia: Reduction in the number of RBCs
Evidenced by decreased: (4 findings)
- Haemoglobin
- Packed cell volume (PCV)
- Haematocrit (HCT)
- Red blood cell count (RBC)
Measurements can help you define the type of anaemia, helping to narrow the cause: (4 groups)
- Mild, moderate, severe
- Normocytic, microcytic, macrocytic
- Normochromic, hypochromic, hyperchromic (artefact)
- Regenerative or non-regenerative
Mild, moderate or severe anaemia:
Based on _______ (may not match clinical presentation)
Severity varies from species to species, depending on normal ______
PCV in the ______ is regarded as a sever anaemia
Don’t stress severely anaemia animals (reduced oxygen carrying capacity)
- PCV
- PCV
- Mid-low teens
Normochromic, hypochromic and hyperchromic anaemia:
Based on the concentration of haemoglobin MCHC/MCH values
- Hypochromic anaemia:
- Hyperchromic anaemia:
- Decreased haemoglobin
- Iron deficiency
- Poor iron concentration (with microcytosis)
- Regenerative anaemias (immature RBCs not fully haemaglobinised)
- Too much haemoglobin
- Not physiologically possible (artefact)
- Normally due to haemolysis of the sample
Normocytic, microcytic and macrocytic anaemia:
Based on MCV values
- Normocytic
- Microcytic
- Macrocytic
- Erythrocytes of unremarkable size:
- Normal MCV value
- Associated with mild non-regenerative anaemia/acute haemorrhage
- Indicates that there is no fundamental problem with RBCs
- Caused by insufficient amount of RBCs - Smaller than mature RBCs
- Low MCV value
- RBC concentration of haemoglobin determines division
- Iron deficiency allows one more division resulting in smaller cells
- Causes include blood loss, PSS, liver disease, dietary insufficiency - Larger than mature RBCs
- High MCV value
- Occurs in regeneration
- Polychromatophils ( young blood cells with large nucleus)
- Can be normal in some breeds (some poodles)
- Can be common artefact in stored blood (RBCs swell over time)
- Can be a sign of bone marrow disorders/present in some FeLV cats
Regenerative vs. Non-regenerative anaemia:
- Regenerative
- Non-regenerative
Important to determine which type - Helps to narrow down cause
- Animal able to respond to the anaemia
- Animal able to up-regulate RBC production
- Body’s response to a fall in oxygenation
- Increased release of erythropoietin from juxtaglomerular apparatus
- Stimulates the bone marrow to increase RBC production
- Usually due to haemorrhage/haemolysis
- Takes 2/3 days for this effect to be seen
- Polychromatophils/reticulocytes increase in the circulation - Animal doesn’t respond to the anaemia
- Bone marrow doesn’t produce more RBCs
- Causes include bone marrow disease, FeLV, renal disease
Polychromatophils/reticulocytes:
Immature RBCs - Indication of regenerative anaemia
Two names but same cells (depending on stain used)
- Polychromatophils - Diff-Quik stain
2. Reticulocytes - Methylene blue stain
Main parts on a blood smear:
- Base/head
- Monolayer
- Feathered edge
Species differences in response to anaemia:
Dogs/cats:
- Expect reticulocyte response
Horses:
- Retain reticulocytes in bone marrow until they have matured
- Bone marrow sample needed (regenerative vs. non-regenerative)
Cattle/sheep:
- Only release reticulocytes from the marrow with severe anaemia
- Not reliable enough for reticulocyte counts
Other features associated with regeneration:
Not as reliable as reticulocyte counts
- Nucleated RBCs
2. Increased Howell-Jolly bodies (nuclear remnants)
Immune mediated haemolytic anaemia (IMHA):
- Primary or Secondary disease (drugs, neoplasia, inflammation etc.)
- Antibodies (IgM/IgG) raised against the animals own RBCs
- RBCs destroyed as foreign
Destruction of RBCs causes noticable morphology changes in addition to what is often a markedly regenerative anaemia.
Agglutinaation?
Rouleaux formation?
Agglutination:
- Strong cell-cell bridges are formed by adherent antibodies
- Produces disorganised aggregations of RBCs
- Saline dilution will not make it disperse (bonds too strong)
Rouleaux formation:
- Lines/stacks of RBCs (‘stack of pennies’)
- Normal in cats/horses
- May be seen with increased plasma viscosity in other species
- Will disperse when diluted (weak hydrostatic bonds)
- Basis of in-saline agglutination test
Ghost cells:
Spherocytes:
Heinz bodies:
Ghost cells:
- Membrane of RBCs ruptured in circulation
- Associated with IgM/complement fixation/intravascular haemolysis
- Can happen with IgG or a mix of both
Spherocytes:
- Ig marked RBCs partially phagocytosed by macrophages
- Remnant re-forms into sphere shape due to lost membrane
- Hard to be sure of in cats (normal anisocytosis - RBC variation)
- Central pallor may also not be present in cats
Heinz bodies:
- Hb oxidised and pushed to cell
