Red Cell Parameters Flashcards
What are the parts of a haematology report?
What do we look for when assessing RBCs?
Red cell mass (PCV, RBCC, Hgb)
Evidence of effective and appropriate erythropoiesis - size and colour (MCV, MCHC, reticulocyte count)
Red cell size and variation (MCV, RDW - red cell distribution width)
Red cell haemoglobinisation (colour) (MCHC)
Red cell shapes and inclusions (smear)
What are we assessing when analysing the erythron?
Is there inadequate, adequate or excessive red cell mass to deliver oxygen to tissues?
What is polycythaemia?
Too many RBCs
relative - lowered fluid content e.g., dehydration, stress
absolute - increased RBCs
Which tests measure the Red cell mass and oxygen carrying capacity of blood?
PCV
RBCC (red blood cell count)
Hgb
- all equally affected by haemoconcentration
- increase and decrease in line so interpreted as a block
When might PCV be calculated wrong in an analyser?
RBCs miscounted:
-mistaken for platelets
- aggregated into pairs and triplets
MCV misleading:
- cell shrinkage or swelling (transport, tube filling, osmotic effect of machine)
What does a high MCHC suggest?
Haemolysis or lipaemia
How does an analyser calculate PCV?
MCV (mean corpuscular volume) x RBCC
What is the rule of three?
PCV = Hgb x 3 (+/-3%)
Describe normocytic anaemia
red blood cells that are normal in size but abnormally low in number
Describe normochromic anaemia
having a normal amount of hemoglobin in red blood cells
Describe macrocytic anaemia
larger than normal red blood cells
Describe microcytic anaemia
Smaller than normal RBCs
Describe hypochromic anaemia
red blood cells are paler than normal caused by a lack of haemoglobin
What does normocytic normochromic anaemia suggest?
Often anaemia of illness or pre-regenerative or occasionally non-regenerative
What does macrocytic hypochromic anaemia suggest?
Classic highly regenerative
Sometimes could just be cell swelling of transport
What does microcytic hypochromic anaemia suggest?
Classic iron deficiency
chronic external blood loss
How is polycythaemia identified?
Increase in PCV, Hgb concentration and RBC count
How can relative polycythaemia be caused?
What is primary polycythaemia?
rare myeloproliferative disorder
abnormal response of RBC precursors
Normal EPO levels
What is secondary polycythaemia?
Chronic tissue hypoxia of renal tissues (low arterial pO2) due to:
heart/lung diseases, high altitude, thrombosis, constriction of renal vessels
Renal tumor or cysts [↑intra-capsular pressure]
Increased EPO
What are reticulocytes?
Young (immature/non-nucleated) erythrocytes prematurely released to blood from the bone marrow in regenerative anaemias.
how can erythrocytes be visualised?
New methylene blue (NMB) precipitation demonstrates RNA-protein complexes (ribosomal RNA & mitochondria).
Young red cells including reticulocytes have “polychromatophil” appearance on Romanowsky (routine) stain
What are the clinical applications of reticulocyte observation?
Evaluation of erythropoiesis in bone marrow.
Differentiation of regenerative and non-regenerative anaemia.
Describe the reticulocytes of dogs
Low number of reticulocytes (<1%)
Expect at least (>60x109/L) in regenerative anaemias
Describe the reticulocytes of cats
Low number of reticulocytes (0.2-1.6%)
Cats have two morphological types of reticulocytes:
- ‘aggregate’ blue stained coarse clumping (0.5% of erythrocytes)
- ‘punctate’ small, blue stained dots (1-10%).
Kinetics of Aggregate vs Punctate means we only consider Aggregate in assessment of regeneration
Expect at least (>50x109/L) in regenerative anaemia
Describe the reticulocytes of ruminants and horses
Virtually no reticulocytes in normal blood;
Reticulocytes may not appear even in very severe anaemias in horses;
In cattle peak production 7-14 days post acute blood loss
Describe the red blood cell morphology of dogs
Larger erythrocytes
Uniform size
Central pallor
Describe the red blood cell morphology of cats
Smaller erythrocytes
Anisocytosis (variation in size)
Scarce central pallor (less concave)
Describe the RBC morphology of horses
Rouleaux
(sedimentation tendency)
Describe the RBC morphology of ruminants
Anisocytosis and crenation (ruffled edge)
Describe variations of RBC morphology between dog breeds
Greyhounds have high PCVs
Akitas have unusually small erythrocytes & particularly high potassium content
Macrocytosis in some poodles
What causes poikilocytosis (alteration in RBC shape)?
abnormal erythropoeisis
specific organ dysfunction
Give examples of different RBC shapes
Codocytes (Target cells, Fe defic)
Spherocytes (IMHA)
Acanthocytes
Schistocytes
Echinocytes (Artefacts) crenation – ‘burr cells’
Give examples of RBC inclusions
Howell Jolly bodies
Basophilic stippling
Nucleated RBC’s
Infectious agents:
- Mycoplasma
- Babesia
- Viral inclusions
Heinz bodies
identify this RBC shape
schistocytes
erythrocyte fragmentation
identify this RBC shape
Acanthocytes
Few irregular elongations of RBC border with rounded ends
identify this RBC shape
Crenation (echinocytes)
Numerous pin-point projections
What is rouleaux formation?
Clustering, sticky, piling of RBCs
Normal finding in horses
Indicates inflammation in small animals
Relates to increased “stickiness” of plasma with increased globulin content
What is agglutination?
Immune-mediated haemolytic anaemia
Caused by mismatched blood transfusion
