Flashcards in Anaemia and Microcytic Anaemias Deck (77)
What is anaemia?
Reduced total red cell mass
Is it easy to measure total red cell mass?
NO - so this is not routinely done
As total red cell mass is difficult to measure, what can be done measured instead?
Outline the Hb and haematocrit levels to diagnose anaemia in adult males.
* Hb <130g/L
* Hct 0.38-0.52
Outline the Hb and haematocrit levels to diagnose anaemia in adult females.
* Hb <120g/L
* Hct 0.37-0.47
Where does red blood cell production take place?
What type of method is used to measure haemoglobin concentration?
Outline the steps in the method of measuring haemoglobin concentration.
* Burst (lyse) the red cells to create Hb solution
* Stabilise the Hb molecules (cyan-metHb)
* Measure the optical density (OD) at 540nm
* OD Proportional to the concentration (Beer's Law)
* Hb concentration calculated against known reference standard cyan-metHb concentration solution
How is haematocrit measured?
The ratio (also commonly expressed as the percentage) of the whole blood that is red cells if the sample was left to settle
In rare situations, haemoglobin/haematocrit are not good indicators of anaemia e.g a rapid bleed and haemodilution
In what situations are Hb/haematocrit not good indicators of anaemia?
* Rapid bleed
Describe why measuring Hb/haematocrit in a rapid bleed is not a good indicator of anaemia.
If 50% of blood volume is lost, the patient will obviously be anaemic as their red cell mass will have dropped by 50%
However, as both blood volume and red cell mass are decreased in proportion to eachother, the concentration of Hb will initially remain the same
True red cell mass is only apparent after a few days once fluid shifts have occurred
If you take measurements too early, you will not see a decrease of Hb
Describe why measuring Hb/haematocrit in haemodilution is not a good indicator of anaemia.
For example, later in pregnancy, plasma volume increases, making Hb concentration lower despite red cell mass being the same
What is increased red cell production known as?
What is a reticulocyte?
A reticulocyte is a young red blood cell, just after it has left the bone marrow
Describe the appearance of a reticulocyte.
* Larger than the average cell
* Contains RNA
* Stains deep purple/red
Up regulation of reticulocyte production by the bone marrow in response to anaemia takes a few days
What can automated analysis of RBC's tell us about RBC's?
* Cell size
* Cell count
* Light-scattering properties
Outline the 3 measured indices of a red cell.
* The haemoglobin concentration
* The number of red cell (concentration)
* The size of the red cells (mean cell volume or MCV)
Outline the 3 calculated indices of a red cell.
* Mean cell haemoglobin
* Mean cell haemoglobin concentration
What does reticulocyte count assess?
Bone marrow response
By which 2 methods is anaemia classified?
* Morphological characteristics
In terms of pathophysiology, anaemia can be classified as either __________ ____ or __________ __________
1. Increased loss
2. Decreased production
What 2 things can decreased production be due to?
* Hypo-proliferation – reduced amount of erythropoiesis
* Maturation abnormality – erythropoiesis is present but ineffective
What are the 2 most common causes of a maturation abnormality, which causes decreased production of red cells?
* Cytoplasmic defects – impaired haemoglobinisation
* Nuclear defects – impaired cell division
Microcytic anaemia has a ____ MCV
Macrocytic anaemia has a ____ MCV
LOW RETICULOCYTE COUNT is seen when?
In a decreased production of red cells
HIGH RETICULOCYTE COUNT is seen when?
In increased loss or destruction of red cells