Interpretation of blood count + Normal ranges

Question 1

Which factors can influence what is normal in medical data?

How does this influence referce range?

Answer 1

Normal for a person can be influeced by both, environmental and genetic factors e.g.

• Age
• Gender
• Physiological status
• Nutritional status
• Ethinic origin
• Altitzde
• Durg abuse (Smoking, alcohol)

Question 2

Explain the process of obtaining a reference range?

Answer 2

Define a sample of healthy volunteers

• sample them
• statistically analise the results:
  
  • e.g. in normal distribution:
    
    • Mean +/- 2SD –> gives rise to 95% range
  • Might require othe statistical test for different distributions

Question 3

What is a health range?

Why can this be necessary?

Answer 3

Health range: range of values that are not within the 95% range/don’t cover all of it but that represent healthy levles

• E.g. high serum lipids are common in western society
• in 95% range: many values would be “normal” but unhealthy

Question 4

How would an Ideal Test/reference range look like?

How does it lood in reality?

Answer 4

Ideal test: no overlap between “healthy”= within reference range and “sick”= abnormal values

In reality: not achieveable

Question 5

Which Values are measured in a full blood count?

Which units are used?

Answer 5

• WBC – white blood cell count in a given volume of blood (× 109/l)
• RBC – red blood cell count in a given volume of blood (× 1012/l)
• Hb – haemoglobin concentration (g/l)
• Hct – haematocrit (l/l)
• PCV – packed cell volume (% or l/l) (an older name for the Hct)
• MCV – mean cell volume (fl)
• MCH – mean cell haemoglobin (pg)
• MCHC – mean cell haemoglobin concentration (g/l)
• Platelet count – the number of platelets in a given volume of blood (× 109/l)

Question 6

How would you interprete a blood count?

Which questions should you ask?

Answer 6

1. WBC and differnetial (different cell in absolute numbers)
   
   • lekocytosis/leukopenia?
   • Why?
   • Which cell is abnromal?
   • Any clues in History?
2. HB and MCV
   
   • Anaemia
   • Clues in blood count
   • large/small cells?
   • Clues in clinical history?
3. Platelet count
   
   • Thrombocytosis/Thrombocytopenia?
   • Clues in blood count?
   • Clues in clinical history?
4. Lood at other values

Might be necessary to look at blood smear (e.g. in sickles cell etc.)

Question 7

What is polycythaemia?

Answer 7

An increased number of erythorcytes

Question 8

What is the difference between pseudo and true polycythaemia?

Answer 8

Psuedo: Reduced plasma volume

True= Too many erythrocytes

Question 9

Which possible causes might casue true polycythaemia?

Answer 9

1. Blood doping/overtransfustion
2. Inappropriate increase of Erythropoetin
   
   • Doping
   • Tumor?
3. Appropriate increase of Erythropoetin i.e. hypoxia
   
   • high altitutde
   • hypoxia due to respiratory diseas
4. Independant of Erythropoetin
   
   • Polycythaemia vera (myleoproliferative neoplasm)

Question 10

What is Polycytheaemia vera?

What are the consequences?

Answer 10

An intrinsic bone marrow disease causing inapropriate increase of erythropoiesis largely independant of EPO

Classified as myeloproliferative neoplasm

–> Leads ot hyperviscous blood and hence to vascular obstructions

Question 11

How would you examine /evaluate a person with polycythaemia?

Answer 11

Clinical history and physical examination

• splenomegaly?
• abdominal mass (tumor)?
• cyanosis?

Compare blood results with appropriate normal range

Question 12

What is the treatment for polycytheamia?

Answer 12

Cause dependant

1. If there is no physical nees or extreme hyperviscosity: removal + thining of blood
2. In intrinsic bone marrow diseae (polycytheamia vera): drug treatment to reduce cell proliferation