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COMMERS > Analytical Studies: case-control Studies > Flashcards

Analytical Studies: case-control Studies Flashcards

1
Q

Purpose of Epidemiology

To _________ community health problems

To identify the ________ and ______ of disease

To plan and evaluate health services

A

diagnose

natural history; aetiology

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2
Q

Strategies in Epidemiology

Epidemiologic __________
Epidemiologic ____________

A

surveillance

research

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3
Q

Epidemiological study designs is divided into 2

List them

A

Observational
Experimental

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4
Q

Observational Epidemiological study designs is divided into 2

List them

A

Descriptive

Analytic

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5
Q

Observational Studies

Investigator observes the __________________ (a “_________ experiment”).

Documents __________ and __________

Documents who does or does not _________________

A

natural course of events

natural; who is exposed

who is non- exposed

develop the outcome of interest

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6
Q

Case series

Descriptive or Analytical?

A

Descriptive

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7
Q

Cross sectional

Descriptive or Analytical?

A

Descriptive

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8
Q

Correlational

Descriptive or Analytical?

A

Descriptive

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9
Q

Case-control

Descriptive or Analytical?

A

Analytical

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10
Q

Cohort

Descriptive or Analytical?

A

Analytical

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11
Q

Clinical trials

Descriptive or Analytical?

A

Analytical

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12
Q

Descriptive Studies
______________________________ of the distribution of a disease, such as ___,____,_____

A

Describe the general characteristics

Person Place Time

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13
Q

Importance of Descriptive Epidemiology

Assess disease _______

Determine presence of an ________

___________ generation

Guide design of ___________

Guide policy

A

trends

epidemic

Hypothesis

analytical studies

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14
Q

Case Reports and Cases Series

__________ of a single patient or a series of patients

Difficult to differentiate between various alternative explanations

Represent ________ in the identification of new diseases or adverse effects of exposures

A

Detailed report

first clues

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15
Q

Most basic type of a descriptive study of individuals are ??

A

Case reports and Case series

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16
Q

Correlational studies

Use data from entire populations to ______________ between _________ during _______ period of time or __________ at _______ points in time

A

compare disease frequency

different groups ; the same

in the same population; different

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17
Q

Correlational studies

Advantages: useful for the __________

Disadvantages: based on _______ and may __________, inability to ______________ at individual level

A

formulation of hypotheses

averages; miss contributing factors

link exposure with disease

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18
Q

Presence or absence of correlation implies valid statistical association

T/F

A

F
Presence or absence of correlation does not imply valid statistical association

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19
Q

Cross Sectional Surveys

Presence or absence of _____________ is assessed at _________ point in time

Provide “ ________ ” of health experience

A

both exposure and disease

the same

snapshot

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20
Q

________ provides a snapshot of healtg experience

A

Cross sectional surveys

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21
Q

Cross sectional surveys

Disadvantage: _________ relationship of exposure and disease is not always _________

A

Temporal

distinguishable

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22
Q

So why proceed to an analytical study?

Often when we need to answer the following type questions:

What is the ___________ for an outbreak of diarrhoeal disease?

What are the _______ for neonatal tetanus?

What ______ are associated with increased mortality for persons with measles?

Does smoking cause lung cancer?

A

source of infection

risk factors

factors

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23
Q

Analytical epidemiology

Done in order to find out if ______________________________

It Attempts to provide the ____? and _____? of health related events.

A

an outcome is related to an exposure.

why; how

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24
Q

Analytical epidemiology

May take the form of
-__________ surveys , where the researcher makes _______ on the population)

  • ___________/________ surveys (_________ on the population,
A

observational; no influence

interventional; experimental

some influence

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25
Q

Analytical epidemiology

May take the form of
- observational surveys e.g ________ studies, ______ studies
- interventional/experimental surveys e.g, in ______ drugs are given)

A

case-control

cohort

clinical trials

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26
Q

Case-control studies

Aetiologic studies in which comparisons are made between individuals.

Individuals who have a disease (____)
Vs

individuals who do not have the disease (______)

A

cases

controls

27
Q

Major Steps in a case-control study

Define and select _____
Select _______
Do __________
Ascertain ————-
_______ analysis and ____ measurement

If exposure is more in cases than in controls then ____________ is suspected

Test any differences for ______ significance

A

cases; controls; Matching

exposures; Comparison; risk

causal association

statistical

28
Q

In creating a case-control study,

Ascertain exposures: Enquiry and record verification for the ________ in both groups

Comparison analysis and risk measurement: ____________ in cases and controls

A

amount of exposure

Compare exposure

29
Q

Selection of cases

Study begins with cases, i.e. the patients in whom ________________________.

all the details of ______________________ are obtained

usually new cases (______ cases) will be chosen either from the ____________ or ___________.

the new cases, which are (similar or different?) clinically, histologically, pathologically and in their duration of exposure (———-) will be chosen to avoid any error and for better comparison.

care in selection of cases is given importance while selecting them to avoid errors in comparison and analysis

A

the disease has already occurred.

their exposure to the suspected cause/causes

incident; general population or from hospitals

Similar; stage

30
Q

Sources of cases
Cases may be chosen either from

•______________ (hospital)
•From —————

A

A single source

multiple sources.

31
Q

What is a control??

A control is as like a case as is possible except that ________________

They must have the same ______________ as a case and must be subject to the same _________ and ________ criteria.

A

they do not have the disease (outcome) in question.

opportunity for exposure

inclusion and exclusion

32
Q

In selecting a control, one control group is optimal for all situations

T/F

A

F

No one control group is optimal for all situations

33
Q

There must be scientific, economic and practical considerations in the selection of controls

T/F

A

T

34
Q

Principles of Control Selection

From (same or different?) study base (target population) as cases

Selected (dependent or independently?) of exposure status!!

If they had developed illness, they would have been a case

“Like should be compared with the like”

A

Same; independently

35
Q

Control should have Comparable information to cases

T/F

A

T

36
Q

Sources for controls

Controls may be obtained either from
•_________
• ________
• ________(———- preferred if available) or
• ________.

A

General population

Hospitals

Relatives; twins

Neighbors

37
Q

General Population Controls

Advantages
– If _______ in general population known – direct __________

Disadvantages
– ______
– ________

A

all cases

calculation of risk

Cost; Sampling frame

38
Q

Neighborhood Controls

Advantages:
– _________ , efficient
– _______ for potentially confounding variables

Disadvantages
– _______ related to neighborhood
– Potential _____

A

Inexpensive; Matched

Exposure; bias

39
Q

Hospital Controls

Advantages:
– _______
– Come from __________

Disadvantages:
– Control disease may be __________
– Hospitalized controls differ from ___________

A

Convenient; same catchment area

linked to exposure

general population

40
Q

Relatives/Friend Controls

Advantages – _______

Disadvantages
–_____
– Friends may share ________

A

Convenient

Bias; same exposure

41
Q

Matching is a comparative technique of ____________________ present in cases and controls, except ______________

A

neutralizing all other variables

the variable (disease) under study

42
Q

Purpose of matching is to eliminate ___________ (______) while conducting the study.

A

systematic errors

biases

43
Q

Limitations of matching

By matching, we can match only the _________________ like __________

Cannot match the ______________ playing a role in causation.

A

known confounding variables like age, sex, occupation etc

unknown confounders

44
Q

Enquiry about exposure

Done ((before or after?) the cases and controls are _______ to the maximum possible extent.

Information is obtained in both groups in a similar manner.

Also involves searching the available records with regard to the exposure to the suspected cause and its duration.

A

After ; matched

45
Q

Biases

__________, or deviation of results or inferences from the truth may arise at any point in the course of study or throughout due to chance.

A

Systematic errors

46
Q

_________ bias is the commonest error usually committed.

A

Selection

47
Q

Selection bias

Either __________ (to some extent) or ____________ or both can minimize it.

A

matching

randomization

48
Q

Confounding due to bias

A confounding variable is A variable which is capable of ____________________

And is also capable of ____________________________.

Allowing ___________________ is confounding bias

A

causing the effect or disease directly on its own

causing the effect or disease indirectly with the association of another factor

this variable into the study

49
Q

Examples for confounding bias

Usually the presence of confounders leads to ____________ e.g. Goitre is seen mostly at high altitudes, but actually, the iodine deficiency at high altitudes is the cause of goitre there.
Similarly, alcoholism is suspected to be the cause of liver cancer but the smoking, which is usually associated with alcoholism may be the confounding variable causing the disease

A

indirect causal associations

50
Q

Examples for confounding bias

_____ is the best

A

Age

51
Q

Information bias

Any error in ____________ i.e. Data about cause will lead to the false inference or results.

This bias is very frequently seen in ___________ studies, as the entire process involved is mostly __________ verification.

A

collecting information

case-control

subjective

52
Q

Memory bias or Recall bias

This is the inability on the part of an individual (case or control) to _____________________

Similarly, patients may ________________ to please the investigator.

A

recollect things that happened in the past accurately.

give wrong information or exaggerate

53
Q

Interviewing bias

Errors can occur while collecting data by interviewing, if the interviewing techniques are ____________ and _________ in a similar fashion and for similar duration for all the cases and controls.

A

not standardized and applied

54
Q

Investigator bias

This is (occasionally or frequently ?) encountered, usually an (intentional or unintentional?) one.

The investigator may conduct interview with one case or a control for a longer time and another for a short time.
The interviewer’s ideas and feelings may unintentionally influence responses while interviewing due to over enthusiasm.

A

occasionally; unintentional

55
Q

Measurement bias

Errors usually occur while ___________ the __________ or ___________.

Measurement bias will occur if measurements are _______________ using similar techniques or methods both in cases and controls.

A

measuring the exposure factor or the suspected cause

not taken in a similar manner

56
Q

Analysis in case-control studies

A

rates

proportions of exposure

57
Q

Analysis for risk measurement

The proportion of the cause in
•the cases (_______)
and in
• the controls (_______)
Are measured.

A

a/a+c

b /b+d

58
Q

________ rates only can be directly calculated from the case-control study design, but not the _____ rates or ________

A

Exposure

incidence

relative risk (RR).

59
Q

Odds ratio aka ____________ ratio (___/_____)

also assesses the risk

A

Cross-product

ad/bc

60
Q

In _____ diseases with (low or high?) incidence, OR is equally as useful as ______
Given that ____ can not be derived from case- control studies.

A

rare ; low

RR

RR

61
Q

Intuitively….
If the frequency of exposure is higher among the cases than the controls,

then the incidence will probably be higher among the ______ than the _______

A

exposed

non-exposed.

62
Q

Strengths of case-control Studies

Useful in ____ diseases with ____ incidence

_____ exposures

(Slow or Rapid?) ,_______ period

(Small or Large?) sample size

No need for ______

Low cost
No ethical issues

A

Rare;low

Multiple; rapid; no latency

Small; follow up

63
Q

Limitations of case-control Studies

No calculation of _____ and ____

Selection of _____ is difficult

Not suitable for rare _______

Problems with _______

A

rates and risks

controls; exposures

mass significance

64
Q

Limitations of case-control Studies

____________________ (main weakness) .

The reliability of the study depends on the ____________.

Problems with recall

Data is collected _________, therefore they are relatively unreliable.

A

Looks at only one outcome

choice of controls

retrospectively

COMMERS (11 decks)

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