WEEK 6 disease prevention, strategies

Question 1

In what levels is Caplan’s prevention model divided? Explain?

Answer 1

1. Primary prevention
   Avois development of disease
2. Secondary prevention
   Early disease detection, to prevent progression and symptoms
3. Tertiary prevention
   (reduce complications, intensity, severity of current disease/care of dieases)

Question 2

What is the target group of universal prevention?

Answer 2

Total population

Question 3

What is the target group of selective prevention?

Answer 3

High risk groups

Question 4

What is the target group of indicated prevention?

Answer 4

Early diagnosis

Question 5

What is the target group of care-related prevention?

Answer 5

Diseased persons

Question 6

Explain the prevention paradox

Answer 6

• Small absolute risk for individuals may have large impact on population health
• Large risk to population health may be a small risk for individual

Question 7

What are 3 divisions in population prevention strategy? Examples?

Answer 7

 Health promotion
- Healthy diet
- Smoking cessation
- Fluoride toothpaste
 Enforcement/regulated
- Product modification
- Bans
- Vaccination
 Health protection provisions:
- Safe roads
- Clean water

Question 8

Explain the high risk approach, give example.

Answer 8

Prevention approach targeted at those who are at highest risk of getting a disease
 Tailored to needs of the high risk group
- Weight loss programs to prevent diabetes
- Drug treatment of high cholesterol

Question 9

What happens with the RR in the population strategy?

Answer 9

 The RR is equally reduced among the whole population.
 Distribution shifts towards the lower risk side

Question 10

What happens with the RR in the high risk strategy?

Answer 10

 The RR is only reduced among the group at highest risk
 Distribution narrows (you get more people in the average risk)

Question 11

For what type of disease is population strategy good vs high risk strategy?

Answer 11

Population:
Useful for common diseases that have a large impact on the general population

High risk:
Useful for targeting spcific exposures

Question 12

Formula of sensitivity for diagnostic test? MEaning?

Answer 12

people true positives/# people with a disease
= probability of a positive test, given that the patient has the disease of interest

Question 13

Formula of specificity of diagnostic test? Meaning?

Answer 13

people true negatives/# people without a disease
= probability of a negative test, given that the patient does not have the disease of interest

Question 14

What questions to ask yourself to determine what makes your test best in terms of sensitivity vs specificity?

Answer 14

• Rather miss few ‘true positives’ or incorrectly identify people as diseased while they are not?

Question 15

What is the positive vs negative predictive value? (PPV, NPV)

Answer 15

 Positive predictive value: probability of disease in a patient with a positive test result
 Negative predictive value: probability that a patient does not have the disease with a negative test result

Question 16

PPV formula?

Answer 16

people true positives/# people tested positive

Question 17

NPV formula?

Answer 17

people that are true negatives/# people with a negative test

Question 18

What does the predictive value depend on?

Answer 18

• Depends on sensitivity and specificity of a test
• Depends on the prevalence of the disease in the population tested

Question 19

What happens to the PPV when the prevalence is very low?

Answer 19

If the prevalence is low, the positive predictive value (PPV) may be very low.
Even when having high specificity and sensitivity, PPV can still be very low, making it not feasible to do this in practice.

Question 20

What is the middle road prevention strategy? For what disease is it often used?

Answer 20

policy between population and high risk, where you want to focus on the population but also want the high-risk approach (e.g. focus on the top half of the population), often used in non-communicable chronic disease risk

Question 21

In what situ is high-risk appr better choice?

Answer 21

When you do not want to subject whole population with a treatment to prevent something that is rare (benefit-to-harm trade-off)
- Rare disease
- Difficult prevention

Question 22

Difference ecological vs cross-sectional study?

Answer 22

you look at group vs individuals

Question 23

Analytical cross-sectional study = ?

Answer 23

study to inform ‘causality of risk factors’

Question 24

What is block randomization?

Answer 24

Block randomization = stratified randomization, especially useful in small study populations where by chance alone an unequal distribution of a risk factor can occur
(separate by gender (stratify) > randomly assign treatment)

Question 25

Reasons to use stratification?

Answer 25

1. See whether there is confounding
2. To see whether there is effect measure modification

Question 26

How can you see from OR and adjusted ORthat something = confounder?

Answer 26

When adj OR is same as crude OR = no confounding