2) Deciding what is normal and interpreting blood counts Flashcards
State some factors that affect what is ‘normal’.
Age Gender Ethnic origin Physiological status Altitude Nutritional status Cigarette smoking Alcohol intake
What is the difference between a reference range and a normal range?
Reference Range = derived from a carefully defined reference population e.g. children 5-10 years
Normal Range = much vaguer – it should represent the people that live in the local area and come to the hospital
How is a reference range determined?
Samples are collected from healthy volunteers with defined characteristics.
The data is analysed by appropriate techniques.
If the data follows a normal (Gausian) distribution, you can determine what is normal by taking the mean and taking 2 standard deviations on either side. Between the 2 SDs on either side, you will have 95% of the data.
What unit is MCV measured in?
Femtolitres (10^-15L)
What unit is MCH measured in?
Picograms (10^-12g)
How are these parameters measured now?
It is determined indirectly by light scattering or by interruption of an electrical field
what is WBC RBC Hb PCV Hct MCV MCH MCHC Platelet count ... measured in
WBC = x 10^9 / l RBC = x 10^12 / l Hb = g / l PCV = l / l Hct = l / l MCV = fl MCH = pg MCHC = g/l Platelet count = x 10 ^ 9 / l
what clinical tests should you do after interpreting a FBC that shows polycythaemia
a young healthy athlete - doping? be v suspicious
a breathless cyanosed patient - probably due to hypoxia
an abdominal mass - could be a carcinoma of the kidney
splenomegaly - a pointer to polycythaemia vera
polycythaemia plus slenomegaly
sign to polycythaemia vera
In a blood count what do you look at
absolute count not the percentage
