Deciding what is normal and interpreting blood counts Flashcards
State 8 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 + 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.
Data with a normal (Gausian): take the mean + 2 SD’s on either side= 95% range
What units are Hb and MCV measured in?
Haemoglobin: g/l
Mean cell volume: Femtolitres (10^-15L)
What unit is MCH measured in?
Picograms (10^-12g)
Mean cell Hb
How are blood parameters measured now?
Determined indirectly by light scattering or by interruption of an electrical field
What is the difference between the MCH and the MCHC?
MCH= amount of Hb per RBC MCHC= amount of Hb per unit volume
What is Polycythaemia?
Too many red cells in the circulation
Hb, RBC + Hct are all increased
State 4 causes of polycythaemia.
Blood doping/ over transfusion
Appropriately increased EPO
Inappropriate EPO synthesis or use
Independent of EPO
When are Hb, RBC + Hct higher and lower physiologically?
Higher in Neonate
Lower in children than in adults
Lower in women than in men
What can cause an high Hb, RBC and Hct other than true polycythaemia?
A decrease in plasma volume
= Pseudopolycythaemia
What are the consequences of polycythaemia?
Hyperviscosity of the blood
Can lead to vascular obstruction
How is polycythaemia treated?
If no physiological need for high Hb/ hyper viscosity is extreme: blood can be removed to thin the blood
If there is an intrinsic bone marrow disease: drugs can be used to reduce BM production of red cells
Why might a health-related range be more meaningful than a 95% range?
Not all results within the normal range are normal e.g. serum lipids in the upper end of this range are common in the west
What is PCV now called?
Hct: Haematocrit
Unit: l/l
