Modules 1 & 2

Question 1

screening criteria

Answer 1

disease
test
treatment
screening programme

Question 2

Bradford Hill criteria

Answer 2

temporality
biological gradient
reversibility
consistency of association
specificity
biological plausibility
strength of association

Question 3

what is a suitable disease (screening)

Answer 3

be of public health importance
- common
- uncommon but early detection can lead to a better outcome (simple treatment)
known history of disease/risk factors
- can detect risk factors/early forms of disease
- has a long pre-clinical phase - long time to detect.

Question 4

what is a suitable test?

Answer 4

reliable
safe
simple
affordable
acceptable
accurate

Question 5

sensitivity

Answer 5

likelihood of a +ve test in those with a disease

true +ve)/(all w/ disease

Question 6

specificity

Answer 6

likelihood of a -ve test in those without disease

true -ve)/(all w/o disease

Question 7

PPV

Answer 7

probability of having disease if you test +ve

true +ve)/(tested +ve

Question 8

NPV

Answer 8

probability of not havig disease if you tested -ve

true -ve)/(tested -ve

Question 9

lead time bias

Answer 9

false impression of increased survival time due to an increase in the time between diagnoses and death compared to clinical diagnosis. Patients may not live longer, instead, they simply know that they have the disease earlier, so live with this knowledge for a longer period of time

Question 10

length time bias

Answer 10

false impression of increased average survival time as screening is more likely to detect a greater proportion of those with a slower progressing form of the disease than a fast progressing form of the disease. thus average survival time of the screened people is skewed and not representative of all the cases, and gives a false impression of survival time.

Question 11

suitable screening programme?

Answer 11

• benefits > harm
• RCT evidence proves increased survival time/decreased mortality rate.
• cost effective
• adequate resources and policy for testing/diagnosis/treatment/program management
• health system must be able to support ALL elements of this pathway
• must be able to reach those who benefit from screening the most.

Question 12

factors to consider in prioritisation

Answer 12

evidence measures
community values and expectations
human rights/justice

Question 13

evidence measure types

Answer 13

descriptive - what is the burden of disease? who has it? trends?
explanatory - where are we now? who is affected most?
evaluative - determinants? risks? why are we getting better/worse? why are there differences in populations?

Question 14

ottawa charder 3 basic strategies

Answer 14

enable
advocate
mediate

Question 15

enable

Answer 15

create opportunities for individuals to make healthy choices

allow access to life skills, supportive environments and information

Question 16

advocate

Answer 16

create supportive environments (political, social, physical, economic, cultural)
achieve equity

Question 17

mediate

Answer 17

bring people with different opinions together to come to a compromise for health care.

Question 18

ottawa charter 5 priority action areas

Answer 18

1. develop personal skills
2. strengthen community action
3. create supportive environments
4. reorient towards primary healthcare
5. develop healthy public policy

Question 19

high risk individual benefits

Answer 19

high individual/physician motivation
cost-effective (only those that need treatment are treated)
appropriate to individuals - tailored to need.
high benefit-risk ratio

Question 20

high risk individual intervention disadvantages

Answer 20

high cost of screening
temporary effect - doesn’t address underlying causes
limited potential - high risk doesn’t mean large burden
behaviorally inappropriate.

Question 21

population intervention benefits

Answer 21

radical - addresses underlying causes
behaviorally appropriate
potential to benefit everyone.

Question 22

population intervention disadvantages

Answer 22

low benefit-risk ratio
low individual/physician ratio
reduced individual benefit

Question 23

strengths RCT’s

Answer 23

minimises confounding - diff characteristics have equal chance of being allocated to either EG or CG. therefore similar baseline characteristics. no other different confounding factors

Question 24

weaknesses RCT’s

Answer 24

maintenance error
highly motivated individuals not representative
costly –> so small study prone to random error

Question 25

cohort study strengths

Answer 25

cheaper

no reverse causality as exposure measured before outcome

Question 26

cohort study weaknesses

Answer 26

confounding - need to adjust

maintenance error

Question 27

ecological study strengths

Answer 27

cheap as data already gathered
good for rare diseases
good for when an exposure is present in large amount s in one popn but not another.

Question 28

ecological study weaknesses

Answer 28

confounding very common.
confounding factors hard to measure and adjust for.
quality of study depends on quality of existing data

Question 29

cross sectional study strengths

Answer 29

no maintenance error

cheaper than RCT’s

Question 30

cross sectional study weaknesses

Answer 30

reverse causality as don’t know temporality between exposure and outcome.
confounding
recall bias/error

Question 31

random error types

Answer 31

sampling error
biological variability
measurement bias
operator ability to take measurements
variation in background noise

Question 32

how to reduce random error

Answer 32

increase sample size
use more objective measuring devices
take averages of measurements.