Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Epidemiology > Study Design Introduction and Case Control Studies. > Flashcards

Study Design Introduction and Case Control Studies. Flashcards

1
Q

What are the 7 functional steps when conducting an epidemiological study?

A
  1. Define the population of interest.
  2. Computerise and create measures of exposures and health indicators.
  3. Take a sample population.
  4. Estimate measures of association between exposures and health indicators of interest.
  5. Evaluate whether this association suggests a causal relationship.
  6. Assess evidence of causes working together.
  7. Asses importance of results and wether they can be applied to other populations.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

When carrying out epidemiological research what do you need to describe in the first instance?

A

The time, place and persons that the disease effects.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

After aetiological factors of a disease have been determined and intervention procedures have been developed what is the next step in epidemiological research?

A

Carry out clinical trials to evaluate the intervention.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is it vital that you do before stating a clinical trial?

A

Define an endpoint.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Primary data is good as it can be amended for varying study objectives, however it is often unfeasible to collect. Why?

A

It is expensive.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Is epidemiology primarily quantitative or qualitative?

A

Quantitative.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What two types of questions are often answered with qualitative studies?

A

Those starting with ‘why’ and ‘how’.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What type of epidemiological study generates theories?

A

Qualitative.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is more important in a qualitative study: the quality of the information or the size of the study?

A

The quality of the information.

In quantitative the amount of information is more important.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Name three methods that can be used to collect qualitative data.

A
  1. Focus group interviews.
  2. Field studies.
  3. Image and documentation analysis.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Name two methods that can be used to collect quantitative data?

A
  1. Observational studies.

2. Experimental studies.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What are quantitive studies usually produced to do?

A

Test theories.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What are observed in field studies?

A

Individuals and communities.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Do descriptive or analytical studies generate hypothesis?

A

Descriptive.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What type of study are case control, case series and cross sectional studies all examples of?

A

Descriptive.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What would a medical professional report in a case report?

A

An unusual disease case.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

If a doctor notices multiple cases of an usual disease what would be produced?

A

A case series.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What sort of exposures are often reported in case series?

A

Occupational based exposures.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Are patterns of disease in case series studies at the population or the individual level?

A

Individual.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Case reports are brief explanations of consecutive unusual disease cases noticed by a medical professional. True or false?

A

False. They are detailed.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Once a case report has been made how can it be used to produce an hypothesis on a wider population?

A

It can lead to the study of medical histories of patients that can trigger the production of new hypothesis.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What is another name for a cross sectional study?

A

A prevalence study.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What can make uncommon diseases look common in a prevalence study?

A

A greater survival rate of the disease.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What two things are measured simultaneously in prevalence studies?

A

Disease and exposures.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

Name three advantages of a cross sectional study.

A
  1. Good for estimating the population burden of a disease.
  2. General population studied.
  3. Good for constant exposures.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

Name three disadvantages of a cross sectional study.

A
  1. Description limited to a specific time point.
  2. Cannot determine is exposure proceeded prevalence.
  3. Influenced by the survival factor of a disease.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

Data collected in a ecological study can not confer something about an individual. Why?

A

Data is at the aggregate/ population level.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

What are ecological studies also known as?

A

Correlation studies.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

What has to be limited for correlation studies to be good?

A

Variation within a population.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

What are compared in ecological studies?

A

Groups, not individuals.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

Ecological studies do not include time intervals. True or false?

A

False, they can look at the same population at different time intervals.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

Ecological studies tend not to be misleading. true or false?

A

False, they can be.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

Name three things that can be studied well in correlation studies.

A
  1. Food availability.
  2. Socioeconomic status and health.
  3. Effect of tax increases in policy.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

Why are ecological studies often cheap?

A

Data often already exists.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

What is the biggest benefit of ecological studies?

A

Exposure is often easier measured at the population level compared to the individual level, eg with air pollution.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

What is ecological fallacy?

A

The failure of ecological data to reflect the true effect of a exposure at the individual level.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

Collinearity is an issue with correlation studies. Why?

A

Some social and demographic factors are correlated more at the population/group level that at the individual level.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

What is the overall aim of analytical studies?

A

To investigate factors leading to the observed distribution of a disease by testing specific hypotheses relating to the aetiology of that disease.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
39
Q

Can ecological and cross sectional studies address analytical hypothesis?

A

Yes, even though they are descriptive studies. This is the case when data is available on an exposure and an endpoint.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
40
Q

Name three examples of an observational study.

A
  1. Case-control.
  2. Cohort.
  3. Nested case control.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
41
Q

What do you not do in an observational study?

A

Interfere with a population.

42
Q

Can cohort or case control studies be retrospective?

A

Cohort.

43
Q

Can incidence rate be determined in case control or cohort studies.

A

Cohort.

44
Q

What is the other name for a cohort study?

A

A longitude study.

45
Q

Cohort studies provide large amounts of useful data that can be used collaboratively. Despite this it would be hard to get funding to start one. Why?

A

A handful of large cohort studies are available and they are exceptionally expensive to do.

46
Q

What was the name of the newest Cohort study in the UK, started in 2006?

A

UK Biobank.

47
Q

For a retrospective study to be produced what is it vital to have?

A

An exposure that is able to be measured in a clear-cut and non biased way.

48
Q

What type of study is best to study rare diseases?

A

Case control.

49
Q

Can you study multiple outcomes in a case control or cohort study?

A

Cohort.

50
Q

Observational studies aim to examine associations. To infer a causal association what is needed to close the causal gap?

A

A plausible mechanism.

51
Q

Do subjects of field trials already have the disease?

A

No.

52
Q

Name the hierachy of evidence (assuming all have been conducted correctly.

A
  1. Systematic review and meta analysis.
  2. Randomised control trials.
  3. Cohort.
  4. Case control.
  5. Cross sectional.
  6. Ecological.
  7. Case reports/ case series.
  8. Expert opinion.
53
Q

Bias primarily happens at the data collecting stage of a study. True or false?

A

False. It can also happen at the analysis and interpretation stage.

54
Q

To be a confounding factor what three things must a confounder be?

A
  1. It must be associated with the disease.
  2. It must be associated with the exposure in different amounts across the exposure groups.
  3. Not on the causal pathway.
55
Q

What sort of relationships do confounding factors mix up?

A

Causal and non causal.

56
Q

Factor 1 is known to be associated with a disease. A positive association is then found with another factor (factor 2) and the disease. In order to test wether this is another associated factor what must you do?

A

See if factor 2 is still associated with the disease in the absence of factor 1.

If this is not the case then factor 2 and the disease are statistically linked, not causally linked.
In this case factor 1 is causal, factor 2 is confounding.

57
Q

At the study design stage what can you do to minimise confounding (4 things)?

A
  1. Randomise individuals to avoid selection bias.
  2. Restrict entry into study so you only compare comparable groups.
  3. Match individuals/ whole populations.
  4. Analyse subgroups separately and adjust the data accordingly.
58
Q

Matching is done at the individual level. True of false?

A

False. It is done at both the population and the individual level.

59
Q

Name four things you can match on.

A
  1. Sex.
  2. Race.
  3. Study centre.
  4. Age.
60
Q

It is harder to match for continuous factors. How can you overcome this problem?

A

Spilt the continuous variables into categories/ brackets.

61
Q

What study design answers the following question?

How common is the finding in a disease?

A

Case series.

62
Q

What study design answers the following questions?

How common is a disease in a population?

A

Cross sectional.

63
Q

What study design answers the following questions?

What explains the differences between populations?

A

Ecological studies.

64
Q

What study design answers the following questions?

What factors are associated with a disease?

A

Case control studies.

65
Q

What study design answers the following questions?

‘How many people will get the disease’, ‘What factors caused the disease’.

A

Cohort studies.

66
Q

What setup is used in the analysis of case control studies?

A

2 by 2 tables.

67
Q

What are the four main stages in a case control study?

A
  1. Select cases with the disease.
  2. Select controls without the disease.
  3. Obtain information on past exposures and other relevant factors.
  4. Compare proportion of exposures in cases and controls.
68
Q

Name 4 design issues of a case control study.

A
  1. Definition of cases and controls.
  2. Selection of cases and controls.
  3. How do you measure an exposure?
  4. How do you account for bias?
69
Q

Name 3 analytical issues of a case control study.

A
  1. What is the strength of association?
  2. Confounding issues.
  3. Logistic regression.
70
Q

What is the main assumption made in a case control study?

A

That the observations seen in the cases and the controls are representative of the whole population.

71
Q

Why are newly diagnosed cases preferable in a case control study?

A

Less recall bias.

72
Q

Some cancers are more likely to be found in particular age groups, for example colon cancer is typically found in the elderly. Why is it hence important to define the case as someone of a certain age?

A

As if an individual gets colon cancer at a younger age it is likely to have a stronger genetic component and be a different disease.

73
Q

Name 3 situations in which cases are not representative.

A
  1. Cases may be regularly undiagnosed in countries that lack screening. Only seeing certain cases.
  2. Endpoints may be misdiagnosed. May not be what you think it is.
  3. When diseases have more aggressive processes. These aggressive cases won’t be represented in the study.
74
Q

Name 5 sources of cases in a case control studies.

A
  1. Hospitals.
  2. Screening clinics.
  3. Disease registries.
  4. Self reporting from the community.
  5. Vital statistic registries.
75
Q

What must a control have the potential to become?

A

A case.

76
Q

Where has this control come from?

A control obtained from a controlled environment at a low cost with minimum recall bias. Characteristics of these individuals may interfere with the exposure being study.

A

A Clinical setting (other diseases may interfere- will be able to tell if they have that disease though).

77
Q

Where has this control come from?

This control has the advantage of potentially having more shared environmental characteristics with the case. This however comes at an expense and allows for the occurrence of recall bias with the potential of every individual not being eligible.

A

The community/ local population.

78
Q

Where has this control come from?

This control has the advantage of potentially having more shared environmental, occupational and behavioural characteristics with the case. Volunteering rate of cases can be lower and these controls may not representive of the larger population.

A

Friends, relatives and neighbours.

79
Q

Self reporting of a case makes bias highly likely. This method does however come with an advantage. What is it?

A

Presence of a disease is pretty much guaranteed.

80
Q

What can minimise bias in self reporting?

A

Getting surrogates to report on the case too.

81
Q

What issue comes with using blood samples when looking at cases in case cohort studies?

A

Blood profiles can change with disease state and may not be representative of the blood profile prior to the disease state.

82
Q

How do you calculate the odds ratio of exposure (2 equations)?

A

odds exposure amongst cases/ odds exposure amongst controls.

(Exposed cases x non exposed controls)/ (Exposed controls x non exposed cases).

83
Q

How do you calculate odds ratio of disease?

A

Odds of disease amongst cases/ Odds of disease amongst controls.

84
Q

What does Woolf’s method state?

A

Ih the 95% CI contains 1 than the odds ratio is not statistically significant.

85
Q

State the equation for working out the 95% confidence interval for the odds ratio.

A

exp(ln(OR)) +/- 1.96 ( 1/a +1/b +1/c +1/d)^1/2

86
Q

OR of (non ordinal category 1) vs (non ordinal category 2) = ?

A

OR non ordinal category 1/ OR non ordinal category 2.

87
Q

What does the Mantel- Haenszel test examine?

A

The trend in disease risk with increasing levels of exposure.

88
Q

What sort of trends does the Mantel- Haenszel test?

A

Linear trends.

89
Q

How do you calculate the expected number of cases in the Mantel- Haenszel chi squared test for ordinal data.

A

(Total number of people in each category x total number of cases)/ Total number of participants.

90
Q

What is are 3 advantages of analysing a continuous variable as an ordinal variable?

A
  1. Cut offs may have biological significance.
  2. Association less effected by skews in the biological data.
  3. Dose dependant relationships can be made clear.
91
Q

If analysis of categorical data shows a linear relationship what is it necessary for you to do?

A

You should analyse the variables as continuous variables in regression models.

92
Q

Splitting linear data into ordinal categories increases statistical significance. True or false?

A

False. Less data is used so statistical significance is reduced.

93
Q

Why does volunteer bias exist?

A

Willingness to volunteer maybe associated with confounding variables or systematic differences compared to the general population.

94
Q

Why is recall bias different in cases and controls?

A

Cases are more likely to recall more factors/ be more inclined to recall more as the results directly effect them.

95
Q

If a patient does not look ill it is favourable to blind the interviewer. Why?

A

They may ask leading questions/ if you’re looking for something you are more likely to find it (outcome bias).

96
Q

Name an example of diagnostic bias.

A

Women on oral contraceptives are more likely to be screened for breast cancer.

97
Q

What is survival bias?

A

Risk can be underestimated because most severe cases die before being identified and recruited.

98
Q

The EPIC study was started in _____. It included ____ subjects and a ____ follow up period.

A

1993, 520,000, 20 years.

99
Q

Name three advantages of case control studies.

A
  1. No loss to follow up.
  2. Results are acquired quickly.
  3. Relatively inexpensive.
100
Q

Name 5 disadvantages of a case control studies.

A
  1. Bias in exposure assessment.
  2. Limited interpretation of causality.
  3. Temporal relationship unclear.
  4. No estimates of incidence of disease.
  5. Only one outcome tested.

Epidemiology (14 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions