Red cell parameters Flashcards
What are the parts of a haematology report?
What are we looking for when assessing RBCs?
Red cell mass
- PCV/Hct, RBCC, Hgb
Evidence for effective & appropriate erythropoiesis
- size & colour (MCV, MCHC)
- reticulocyte count
Red cells size & variation
- MCV, RDW
Red cell haemoglobinisation (colour)
- MCHC
Red cell shapes & inclusions
- smear
What are we assessing when evaluating the erythron?
Is there inadequate, adequate or excessive red cell mass to deliver oxygen to tissues?
Is there evidence of anaemia?
Is there evidence of polycythaemia?
What is polycythaemia? What are the types?
Too many RBCs
relative - Apparent increase in RBC due to decrease in fluid in circulation (often increase total protein & albumin)
absolute - True increase in RBC mass due to increased RBC production/release
Which parameters measure red cell mass & oxygen carrying capacity?
PCV
RBCC (red blood cell count)
Hgb
- all equally affected by haemoconcentration
- increase & decrease in line so interpreted as a block
How is PCV calculated?
MCV x RBCC
When might PCV be calculated wrong in an analyser?
RBCs miscounted:
-mistaken for platelets
- aggregated into pairs & triplets
MCV misleading:
- cell shrinkage or swelling (transport, tube filling, osmotic effect of machine)
What does a high MCHC suggest?
Haemolysis or lipaemia
What is the rule of 3?
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 haemoglobin 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 (occasionally non-regenerative)
What does macrocyctic 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 & RBC count
What are some causes of relative polycythaemia?
Dehydration
Exercise/fear/excitement/severe pain - stress
- Adrenaline secretion, splenic contraction & transient redistribution of RBC from spleen to circulation
Resolves after rehydration or removal of cause of splenic contraction
What are some causes of absolute polycythaemia?
Primary polycythaemia:
- rare myeloproliferative disorder
- abnormal response of RBC precursors
- Normal EPO levels
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 erythrocytes prematurely released to blood from bone marrow in regenerative anaemias
How can reticulocytes be visualised?
New methylene blue (NMB) stain: highlights reticulocytes by precipitating ribosomal RNA and mitochondria as a visible network.
On Romanowsky stain (routine), they appear as polychromatophilic (bluish tint) young red cells
What are the clinical applications of reticulocyte observation?
Evaluation of erythopoiesis in bone marrow
Differentiation of regenerative & non-regenerative anaemia
Describe reticulocytes of dogs
Low number of reticulocytes (<1%)
Except >60x10^9/L in regenerative anaemia
