S3) Full Blood Counts Flashcards
What percentage of healthy people are outside the normal range?
5% - 2.5% above and below
Which factors cause the normal range to vary? (4)
Age
Sex
Ethnicity
Co-morbidities
Why are FBCs interpreted in context of previous FBCs?
To show whether there has been an acute/ chronic change
Errors:
Specimen collection (3)
Specimen mix up
Pooling samples
Poor technique
Errors:
Specimen delivery (2)
Specimen delayed/ not delivered
Wrong delivery method
Errors:
Specimen analysis and result reporting (2)
Wrong test requested / performed
Technical error
Errors:
Responsive action (2)
Result not reviewed
Reflex tests not carried out
What must be done to the sample before testing and why?
K-EDTA anticoagulated to chelate calcium ions and stop blood coagulation
Which 3 analyser techniques are used?
Spectrophotometry
Flow cytometry
Flow cytometry differential
What is packed cell volume (PCV/ haemotocrit)
When is it depressed/ elevated?
How is the PCV reduced?
The proportion of blood that is made up of RBCs
Depressed in anaemia, elevated in polycythemia
The PCV in polycythemia is reduced by venesection or drug treatment
What is RCC?
When is it reduced or increased?
Red cell count - number of RBCs in a given volume of blood
Reduced in microcytic anaemia caused by iron deficiency and increased in microcytic anaemia caused by thalassemia
What is the MCV?
What is it used to detect?
Mean cell volume - mean size of an RBC
Used to screen the cause of anaemia
What is RDW?
When is it increased?
When is it normal?
Red cell distribution width - shows variation in the size of RBCs
Increased in anisocytosis (unequal width of cells), iron deficiency and following transfusion
Normal in thalassaemia
What is MCH?
When is it reduced?
When is it normal/ increased?
Mean cell haemoglobin - average amount of haemoglobin in each RBC
Iron deficient
Macrocytic anaemias
What is MCHC?
How is it calculated?
When is it increased?
When types of infections is it useful to identify?
Mean cell haemoglobin concentration
Hb/MCV x RCC
Spherocytosis
Viral or mycoplasma
When would a blood film be requested? (3)
What is the process of taking a blood film?
Significantly outside normal range
Significant change
Abnormal cells - immature and unable to identify
Small drop of blood onto glass slide - 1 cell layer thick
Fixed with methanol
Stained to allow visualisation under microscope
What do the following terms mean?
Micro/macrocytic
Hypo/hyperchromic
Small / large RBC
Less / more Hb
What do the following terms mean?
Dimorphism
Two distinct populations of red cells
What do the following terms mean?
Poikilocytosis
Abnormally shaped RBC
What do the following terms mean?
Echinocytes, acanthocytes, keratocytes, schistiocytes
Spiculated cells
What do the following terms mean?
Target cells
RBC with dark area in the middle
What do the following inclusions mean?
Howell-Jolly bodies
Basophilic stippling
Pappenheimer bodies
Heinz bodies
Haemoglobin inclusions
DNA/ nuclear fragments
RNA inclusions
Iron inclusions
Denatured haemoglobin
Denatured haemoglobin H
Which cells are detected in the WBC differential? (5)
Neutrophils
Eosinphils
Basophils
Lymphocytes
Monocytes
Which conditions / substances affect platelet levels?
Infection, iron deficiency and drugs
