case control

Question 1

did the observer assign the exposure :
1- if yes then its – studies :
-if yes to random allocation then —- trail
- if no to random allocation then its — trial
2- if no then its — studies
- if yes to comparison groups then its — study which includes ecological case control cohort and cross sectional study
- if no then its — study as cohort and cross sectional

Answer 1

intervention
randomised trail
non randomised trail
observationa;
analytic study
descriptive study

Question 2

case control study:
A study that compares — groups of people: those with the disease or condition under study ( aka — ) and a very similar group of people who do not have the disease or condition ( — ).
Purpose is to examine association between an — (s) and an —
Four key steps:
1- identity — the people with the disease or outcome
2- Identify the—- – the people who do not have the disease or outcome
3- Measure — (e.g. potential risk factors for the outcome) among the cases and controls
4- — whether or not the cases are more likely to have been exposed to a risk factor than the controls

Answer 2

2
cases
controls
exposure and outcome
cases
controls
exposure
analyse

Question 3

all people in the population who have the outcome e.g. lung cancer is identifying —-
- a representative sample of the study population without the outcome e.g. no lung cancer is - identifying —
- Individuals are selected from a — population on the basis of their disease/condition status

Answer 3

cases
controls
defined

Question 4

when cohort study fails :
If the outcome is —
If the outcome takes a — to develop
Very few people will develop the outcome
A very long — period (possibly decades) would be needed
Cohort studies become very — and — to conduct
You might never identify enough people with the outcome to make meaningful conclusions

Answer 4

rare
long time
follow up
expensive and difficult

Question 5

identifying cases:
Must have a clear —
Definition should be — and — to all cases
Can be based on — or — definition
Must describe carefully how cases are —
selecting controls:
Selection of appropriate — is often the most demanding and difficult part of a case-control study
Controls should be representative of the — from which the cases have arisen. But they should be without the — or—.

Answer 5

case definition
replicable and applied
clinical or laboratory
selected
controls
population
disease or outcome

Question 6

selecting controls:
-Need to understand from what population the cases arose from
-Sources of “population controls” or “population-based controls” include:
population —
— rolls
— databases
-Often more than — control is selected for each case
-This increases — power
-In other words, we say there is evidence of an association when there really is an— – we reach the right conclusion

Answer 6

population registers
electoral rolls
general practice
more than one
statistical
assosiation

Question 7

measuring exposures :
-Data on exposures can be measured in a variety of ways e.g., by — , reviewing medical —, using biological — .
-As with all studies you need to use a method that is – and — to measure the exposure (and indeed the outcome).
-Case-controls studies are often not suitable to use when the exposure is — .

Answer 7

interviews
records
samples
valid and reliable
rare

Question 8

advantages of case control studies:
Useful for rare — (i.e. — )
Useful for diseases with —
Often — and — than cohort studies
Can study association between— exposures and an outcome
Can conduct expensive or time-consuming tests, which may not be possible with a — study

Answer 8

disease or outcomes ( but not exposures )
long latency
cheaper and quicker
mutiple
cohort

Question 9

summary of sources of errors:
all apply to case control studies
1- selection of participants as sampling —-
2- measurement - instrument as self-administered questionnaire, monitor, interview is —-
3- measumenet - observer is —-

Answer 9

sampling error or selection bias
inaccuracy ( poor validity or poor reliability )
between or within observers

Question 10

selection bias:
Controls are not representative of the population that cases come from
Particularly arises if using — controls
Hospital controls are usually people who are patients at the same hospital(s) as the cases who do not have the disease
Have to ensure that
-There are no health-care access issues that prevent hospital controls being representative of the population
-The disease for which they were admitted is not related to risk factors for the outcome of interest
-The distribution of exposures in the hospital controls may differ to the distribution of exposures in the population that cases came from

Answer 10

hospital

Question 11

observer bias aka interviewer bias:
Often information on exposures is collected by —
Interviewers knowing whether they are talking to a case or a control may change how they collect data on the exposure
To minimise observer bias:
- – interviewers and use — questioning
- — interviewers to whether a person is a case or control
- Limit — among interviewers about the hypothesis being tested (e.g., don’t tell them which exposure is of most interest)
- Cases may describe their level of exposure differently than controls, even if there is no difference
Having a disease may make people more aware of an exposure or the importance they attach to it this is known as – bias
we can minimise it by blinding – and controls to the —

Answer 11

interview
train
standardised
blind
limit knowledge
recall bias
cases
research question

Question 12

As with all observational studies, an apparent association between an exposure and outcome may be due in part or whole to a third factor
is known as —

Answer 12

cofounding

Question 13

analysing a case control study :
In a case control study we specifically include the people with the — ( unlike cohort)
Don’t start with a representative sample of the population and see who has the outcome
Don’t start with a representative sample of the population who don’t have the outcome and see who develops it
-Can’t calculate — or —
-Can’t calculate —

Answer 13

outcome
prevalence or incidence
relative risk

Question 14

In a case control study we can only calculate an —
The odds ratio is the odds of — among the — compared to the odds of — among the —
The odds ratio is a good approximation of the —

Answer 14

odd ratio
exposure among cases
exposure among controls
relative risk
so basically:
odd ratio = odd of exposure among cases/ odd of exposure among controls
check example slide33

Question 15

effects of confounding:
2- Create an — association when one does not exist
E.g., odds ratio for association between asthma and Covid-19 ICU admission is 2.84. If we controlled for educational level somehow, the odds ratio might be 1
2-Over- or under-estimation of the — of the true association
E.g. odds ratio for association between asthma and Covid-19 ICU admission is 2.84. If we controlled for educational level, the odds ratio might be 2.00
3- Hide a — if it exists
E.g., if we found the odds ratio for association between asthma and Covid-19 ICU admission is 1 when we don’t control for educational level, and it becomes 2.84 when we do control for educational level. Asthma and Covid-19 ICU admission are associated, but the association is hidden unless we control for educational level
4. — the direction of the association (Simpson’s paradox)
E.g., odds ratio for association between asthma and Covid-19 ICU admission is 2.84. If we controlled for educational level, the odds ratio might become 0.9 (i.e., the association goes from a positive association to a negative association)

Answer 15

apparent
size
true association
reverse

Question 16

dealing w confounding:
1- Design a — in a way that minimises the effect of confounding factors
— : restricting the sample to people with or without the confounding variable,
— : matching cases and controls for potential confounding factors, makes them more similar with respect to potential confounding factors.
- —-
2- Use — methods for adjusting the effects of confounding
-Multivariable analysis using — techniques
-Stratification (or post–stratification): splitting the sample into — according to their level of the confounding variable (e.g. smokers and non-smokers) and estimating the association between the exposure and outcome for each strata

Answer 16

study
restriction
matching
randomisation
statistical method
regression
strata

Question 17

mutlivariable regression:
Adjusts the — effect of an — on an outcome for the effect of other potentially confounding factors.
Hence, derive an estimate of the — effect of the exposure of interest
Provides “— ” effect (e.g., adjusted odds ratio)

Answer 17

estimated
exposure
independent
adjusted