Prevention

Question 1

What are the types of prevention?

Answer 1

Primary – intervention to prevent onset of disease
Secondary – intervention to pick up asymptomatic individuals with disease and treat
Tertiary – intervention to reduce negative effects of disease from symptomatic individuals

Question 2

Define screening.

Answer 2

Process which sorts out apparently well people who probably have a disease

Question 3

What is the Wilson and Jungner Criteria?

Answer 3

1. Condition
   Important health problem
   Can be detected at an early stage
   Well understood natural history
2. Screening test
   Acceptable
   Suitable
3. Treatment
   Effective
   Agreed on who to treat
4. Organisation
   Cost effective
   Facilities
   On-going process

Question 4

Define sensitivity.

Answer 4

Proportion of people with the disease to be correctly identified by the test

Question 5

Define specificity.

Answer 5

Proportion of individuals without the disease to be correctly excluded from the results of the test

Question 6

Define positive predictive value.

Answer 6

Proportion of people with a positive test who actually has the disease

Question 7

Define negative predictive value.

Answer 7

Proportion of people with a negative test who do not have the disease

Question 8

Define lead-time bias.

Answer 8

Overestimation of survival duration due to earlier detection by screening instead of onset of clinical symptoms
You think screening increase survival, but actually it’s only cause you pick up earlier. No change in mortality

Question 9

Define length-time bias.

Answer 9

Overestimation of survival duration due to relative excess of cases detected that are slowly progressing
You think you detect more cases because of screening, but actually its because the disease is slow progressing

Question 10

What is population approach to prevention?

Answer 10

The population approach is a preventative measure delivered on a population wide basis and seeks to shift the risk factor distribution curve
e.g. dietary salt reduction through legislation, working with the food industry and advice to the general public should shift the blood pressure distribution curve to the left

Question 11

What is high risk approach to prevention

Answer 11

The high risk approach seeks to identify individuals above a chosen cut-off and treat them
e.g. screening for people with high blood pressure and treating them

Question 12

What is the prevention paradox?

Answer 12

“A preventive measure which brings much benefit to the population often offers little to each participating individual.”

Eg

“If all male British doctors wore their car seat belts on every journey throughout their working lives, then for one life thereby saved there would be about 400 who always take that preventive precaution.

399 would have worn a seat belt every day for 40 years without benefit to their survival.”