Red cell parameters Flashcards
what are you looking for when assesssing RBC?
- Red cell mass
(PCV/Hct, RBCC, Hgb) - Evidence for effective and appropriate erythropoiesis
size and colour (MCV, MCHC)
reticulocyte count - Red cells size and variation
(MCV, RDW) - Red cell haemoglobinisation (colour)
MCHC - Red cell shapes and inclusions
Smear
what does MCHC stand for and what does it mean?
Mean corpuscular hemoglobin concentration - how much haemoglobin is in the red cell
what is polycythaemia?
high number of red blood cells in blood
can be relavtive or absolute
what is relative polycythaemia?
Apparent increase in RBC due to a decrease in fluid in circulation (often increase total protein and albumin)
PCV has increased but not RBC production (dehydration)
what is absolute polycythaemia?
True increase in RBC mass due to increased RBC production/release (usu polychromasia, anisocytosis and reticulocytes)
what is the opposite of polycythaemia?
anaemia
what are the two types of anaemia?
regenerative or non-regenerative
what are the 5 cellular charateristics of anaemia?
normocytic, normochromic, hypochromic, macrocytic, microcytic
what is the other initials for packed cell volume?
Hct - hematocrit test
what are the three tests that tell you how many red cells there are? (red cell mass)
PCV, RBC Count, HgB conc
* All three are measures of red cell mass and oxygen carrying capacity
* Usually interpret them as a block
* All equally affected by haemoconcentration
* Will usually increase and decrease in line with one another
* When they are discordant (dont match) find out why – “rule of three”
why can PVC from an analyser be wrong?
PCV is calculated rather than measured in an analyser (PCV = MCV xRBCC)
PCV may be wrong if:
* RBC’s miscounted
* Mistaken for platelets
* Aggregated into pairs and triplets
* MCV misleading
* Cell shrinkage or swelling
* Transport, tube filling
* Osmotic effects in machine
MCV - mean corpuscular volume
why might the MCHC be high ?
- Haemolysis (sample handling or intravascular) - Hgb is outside the cells
- Lipaemia - interferes with light through sample, affects Hbg measuring
Not physiological to cram more Hgb into red cells than they will take
what are the reasons that MCV is wrong?
- Swelling of transport
- Mis-identification – pairs and triplets, cross over with large platelets
- Cell shrinkage or expansion in sample e.g. hyperosmolar
- Will impact on calculated PCV/HCT
what is the rule of three for red cell mass?
Hematocrit % approx = Hgb (g/dL) x3 (+/-3%)
or can be picked up by looking at the MCHC, will show when RBC, HCT and HGB are not mathcing
what is analysis results is the classifiction of anaemia based on?
Based on MCV and MCHC
* Blunt measure - a lot of immature cells (bigger) are needed before the average cell volume will increase enough to be outside of the reference limit - smear reading might be better at recognising immature cells
* Microscope visible findings may not be sufficient to push parameter out of reference range - this is why visual exam is important
* Machine dot-plots and histograms more sensitive
what is often the reason for normocytic normochromic anaemic?
illness or pre-regenerative or occasionally non-regenerative
what is the reason for macrocytic hypochromic anaemia, why is this the apperance/structure?
classic highly regenrative
- lots of immature larger RBC, normal amount of haemoglobin but due to larger space, the colour is pale
what is the reason for microcytic hypochromic anaemia?
iron deficiency, chronic external blood loss
there is not enough iron to make enoguh Hgb to stop the red cells devision - therefore small red cells
what is the reason dor microcytic hypochromic RBCs without anaemia?
portosystemic shunt - as iron not an avalible as it should be
what are the causes of absolute polycythaemia?
- tumour
- bone marrow
- more erythropoietin (kidney tumour and hypoxia (altitude training))
Exercise, fear, excitement, severe pain - (stress ) can cause a relative polycythaemia, why is this?
Adrenaline secretion, splenic contraction and transient redistribution of RBC from the spleen to the circulation
what is the cause of primary polycythaemia (polucythaemia vera)?
- rare myeloproliferative disorder (affecting) the bone marrow
- abnormal response of RBC precursors
- Normal EPO levels
what is the cause of 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
why can Renal tumor or cysts cause seconday polycythaemia?
↑intra-capsular pressure - less blood able to pass through, sensors that check oxygention levels for erythropoietin production, think O2 deficiency therefore increases erythropoietin production and increaased RBCs
