Flashcards in Full Blood Count Deck (17)
What are the components of blood
- 55% plasma
- 45% erythrocytes
What are two automated test methods for doing a full blood count?
a) Aperture Impedance
b) Light Scatter (laser)
How is haemoglobin measured?
NOT measured by cell sorter
- RBCs lysed and light absorbance is measures
How is the Red Cell Count measured?
number of cells through light source
How is the Hematocrit measured?
– measures % of blood taken up by red cells
- summation of number of pulses and average pulse height
What is the RDW (Red Cell Distribution Width)?
Red Cell Distribution Width (RDW)- measure of the range of variation of red blood cell (RBC) volume
i) RDW-SD – when reported as standard deviation
- calculates the wide at the 20% height levels of the histogram to find MCV
ii) RDW-CV – when reported as coefficient of variation
- reference range = 11.5-14.5%
How are reticulocytes singled out for automated measures?
Why are they measured?
Can target RNA with dye as reticulocytes have more RNA than mature RBC.
Measurement used to check for:
- increased in haemolysis/acute bleeding
- BM failure/CRF/B12/fol/Fe deficiency
How are white cells distinguished from red cells to measure white cell count?
What are some potential errors that could occur despite this distinguishment?
RBCs are discriminated from platelets by size and then lysed.
- large platelets
- white cell agglutination
- NRBCs (nucleated RBCs)
What are the 5 different white blood cells that can be measured in a WCC and how are they distinguished from each other?
Can get 5 part differential:
- complexity/light scatter
- fluorescence after labeling
What can the mean platelet volume tell you?
Younger platelets are smaller so can tell you about age
What are some factors that could cause bad results for RCC or WCC?
- cold agglutinants - increases MCV and MCHC
- lipemia - high lipid levels causes turbidity and increases Hb and MCH
- Nucleated RBCs - will be counted as white cells
- High WCC - can result in high Hb, RCC and RBC indices
- platelet clumps - decreases platelets but increases WCC
What 2 factors cause cytopaenias (low cell counts)?
a) lower production
b) higher destruction
What are the 3 broad categories of anemia?
a) Microcytic - presence of small, often hypochromic, red blood cells in a peripheral blood smear and is usually characterized by a low MCV (small and pale).
- Iron deficiency
- chronic disease
- rare causes
b) Macrocytic – large RBCs
- megaloblastic (B12 or folate deficiency) and non-megaloblastic
c) Normocytic – normal MCV, but decreased Hb and hematocrit.
- BM Failure
What are some of the clues in blood of iron deficiency?
- thrombocytosis (too many platelets)
- low RCC
- high RDW (RBC volume)
- Blood film: pencils, elliptocytes, target cells.
What are the symptoms of thrombocytopenia? (platelet deficiency)
- Oozing and bruising
- Cutaneous mucosal bleeding
- Prolonged bleeding from wounds
- Internal bleeds – rare until less than 10.
What are the causes of thrombocytopenia? (platelet deficiency)
a) Failure of platelet production, i.e. BM failure, selective megakaryocyte depression and hereditary problems
b) Increased destruction:
- drug induced
- DIC or TTP: microangiopathic process (Disseminated intravascular coagulation and Thrombotic thrombocytopenic purpura)
- immune – alloantibodies (neonatal and transfusion) or autoantibodies