Defining disease and normality

Question 1

What is the definition of abnormality?

Answer 1

Different from what is usual or average, especially in a way that is bad

Question 2

What are the 3 features of abnormality?

Answer 2

• abnormal if unusual
• abnormal if associated with clinical
  abnormality
• abnormal if increased risk of future disease

Question 3

What is diseased influenced by?

Answer 3

Disease is an absolute or relative concept, influenced by evidence of symptoms.

Question 4

What is the statistically normal reference range in laboratory testing?

Answer 4

Normal values = 95%

Too high = 2.5%
Too low = 2.5% –> statistically abnormal

• by definition 5% of healthy people will have
  abnormal ‘unusual’ values

Question 5

What does it mean by abnormal as increased risk of future disease?

Answer 5

• We must think in terms of the probability of disease being present, rather than the certainty
• e.g. blood pressure levels that are not
  ‘abnormal’ in the UK ( “abnormal if unusual”)
  are nonetheless associated with increased
  risk of mortality and morbidity in the future