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Revision > Epidemiology > Flashcards

Epidemiology Flashcards

1
Q

Definition of incidence

A

Number of NEW cases within population @ risk

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2
Q

Prevalence is :

A

No. of old + new cases within population at risk

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3
Q

Absolute risk (AR):

A

Number of events (good or bad)*
___________________________
Population within that group

*in treatment or control groups

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4
Q

Relative risk :

A

Exposed
________
Non-exposed

Or
AR treatment group/ AR control group

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5
Q

Absolute risk reduction (ARR)

A

AR control (placebo) group - AR test (treatment)

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6
Q

Relative risk reduction (RRR)

A 
ARC -ART
\_\_\_\_\_\_\_\_\_
ARC 
Or
1-RR
ARC= AR of control group ART= of treatment group 
RR= ART/ARC
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7
Q

Sensitivity

A

True positive
________________________
True positive + false negative

= A/A+C

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8
Q

Specificity

A

True negative
_______________
True negative + false positive

=D/D+B

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9
Q

Number needed treatment

A

Average no.of patients that need to be treated to prevent 1 additional bad outcome
NNT=1/ARR (inverse of absolute risk reduction)

E.g number of pets that need to be treated for one of them to benefit compared with control

Lower the NNT the better the drug

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10
Q

1 standard deviation =

A

68.2

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11
Q

2SD=

A

95.4

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12
Q

3SD=

A

99.7

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13
Q

What are examples of measures of central tendency

A

Mean
Median
Mode

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14
Q

What are examples of measures of dispersion

A

Standard deviation

Standard error of mean

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15
Q

Positive predictive value (PPV) =

A

True positive
___________
TP + FP

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16
Q

Negative predictive value =

A

True negative
_____
FN +TN

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17
Q

Accuracy =

A

(True +)+(true -)
______________
TP+FP+TN+FN

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18
Q

Name an interventional study.

A

Randomised controlled trial

19
Q

Types of observational studies

A

Prospective cohort study
Snapshot - cross sectional study
Retrospective

20
Q

Retrospective case study types

A

Case control - starts with disease

Retrospective cohort - starts with exposure

21
Q

Study that involves only the present

A

Cross sectional (snapshot)

22
Q

Study that involves :present —> future

A

Prospective cohort

23
Q

Study that involves past

A

Case control study
- 2 groups = one with disease/outcome & 1 w/o
Look back to assess statiscally significant difference in rate of exposure

24
Q

Main outcome measure in case control studies

A

Odds ratio

25
Q

Advantages of case control studies (5)

A 
Cheap 
Quick & easy to conduct 
Good for disease with long latency periods
Can asses multiple exposure
Good for rare disease
26
Q

Disadvantages of case control studies (4)

A

More prone to bias - main expose is recall bias
Can only asses 1 outcome or disease
Cannot establish risk
Cannot establish prevalence

27
Q

Case control vs cohort

A

cOhOrt - relatives are the same (relative risk is the same)
- usually prospective, look forward in time, however can be retrospective

cAse cOntrol - vowels at odds with another = Odds ratio
Start with disease and look back in time

Cohort - start with exposure
Case control - start with disease

28
Q

What are cohort studies good for

A

Assessing prognosis RFs and harm

29
Q

Outcome measure in cohort studies

A

Relative risk ratio or relative risk

30
Q

Advantages of cohort studies (4)

A

Usually prospective
Can establish risk directly
Can assess multiple outcomes and diseases
Good for rare exposures

31
Q

Disadvantages of cohort studies (4)

A

More expensive
Longer/harder to conduct
Not good for rare diseases
Not good for diseases with long latency periods

32
Q

Case control vs retrospective cohort

A

Both retrospective
CC- starts from outcomes and tries to study what the exposure was
(Starts with disease)
RC - starts with exposure
Exposure already determined - tries to study association to disease

33
Q

High sensitivity =

A

Few false negatives

34
Q

Low sensitivity =

A

Many false negs

35
Q

High specificity =

A

Few false positive s

36
Q

Low specificity =

A

Many false positives

37
Q

Reasons for dropout from study

A

Dropouts more in placebo -
- breakdown of double blind study. Or group in blinded trial accidentally revealed to researchers

If similar dropout numbers in both - possible chance event

38
Q

Relative risk reduction =

A

1 - RR
Or
ARC-ART/ARC

39
Q

Types of randomised control studies

A

Single blinded
- either researchers or candidates don’t know who’s using real tx
Only one of them is blind top the information

Double blinded
Noth candidates and researchers are blind to the information

40
Q

Number needed to treat=

A

1/ ARR

ARR= ARC -ART

41
Q

Secondary attack rate

A

No. Of 2ry cases
_______________
(All people in group - 1ry cases)

42
Q

Primary attack rate

A

No of 1ry cases/ total population at risk x 100

43
Q

Accuracy of a screening test

A

True positives + true negatives
____________________________
TP+TN+FP+FN

44
Q

Number needed to harm is

A

No of people who have to take a treatment for 1 of them to have an adverse effect

Revision (31 decks)

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