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RESS Notes Flashcards

1
Q

Representative sampling

A

Choosing a sample representative of whole population

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2
Q

Exposure

A

Something participants are exposed to, an attribute or a behaviour

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3
Q

Outcome

A

Result being investigated

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4
Q

Variable

A

Characteristic that differs between individuals and can be measured

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5
Q

Dependant variable

A

variable that changes based on changes to another variable

ie the outcome

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6
Q

Independent variable

A

variable that causes changes in other variables

ie the exposure

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7
Q

Proxy variable

A

not normally of interest but has close correlation to variable of interest

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8
Q

Confounding variable

A

interferes with relationship between dependent and independent variable (causes outcome and exposure)

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9
Q

Mediator

A

State that occurs between exposure and outcome - no effect on outcome
Do not adjust for mediators

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10
Q

Competing exposure

A

Different exposure that causes same outcome

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11
Q

Nominal data

A

Categorical eg marital status

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12
Q

Ordinal data

A

Categorical in order ie good, very good, excellent

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13
Q

Discrete data

A

Quantitative, whole numbers

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14
Q

Continuous data

A

Quantitative, on a continuum

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15
Q

Data collection proforma

A

Questionnaire to ensure variable are consistently and accurately measured

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16
Q

Linear modelling

A

Indicates if there is an association between 2 variabls

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17
Q

Confidence intervals

A

Range of values within which researches are confident that the results of repetition of the study would fall
When applied to odds ratios, if CI includes 1 then conclusion is that exposure is not related to outcome

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18
Q

Confidence level

A

probability that repeated results will fall within confidence intervals

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19
Q

Number needed to treat

A

Average number of patients who need to be treated to prevent one additional bad outcome
Ideal = 1
Lower the better

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20
Q

Number needed to harm

A

average number of patients who need to receive treatment in order for one bad outcome to occur

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21
Q

Absolute risk

A

Difference between control group’s event rate and experimental group’s event rate

22
Q

Relative risk

A

AKA risk ratio

ratio of probability of an event occurring in exposed group to the probability in the non exposed group

23
Q

Odds ratio

A

Used to quantify how closely linked an exposure and an outcome are

>1 = association more likely in control group
1 = no difference to control group
<1 = association less likely in control group
24
Q

Adjusted odds ratio

A

Odds ratio after adjusting for confounding variables and competing exposures

25
P value
Probability of obtaining a result as extreme as the one observed, given the null hypothesis is true P <0.05 = statistically significant P >0.05 = not significant
26
Randomised control trials
Participants are randomly allocated to receive treatment or not Can be double blind, single blind or non blind
27
What observational studies are there?
Cohort Cross sectional Case control Ecological
28
Cohort study
Analysis of risk factors, follows cohort of people without disease who share characteristic over period of time Can be prospective - will control all testing but can lose patients in follow up Can be retrospective - immediately available data but can only examine prognostic factors Can be time series - repeated observation of the same variables in the a cohort at designated points in time
29
Cross sectional
Collect data from population at particular point in time Descriptive studies Used to describe odds ratios, absolute risks and relative risks Useful to analyse prevalence
30
Ecological study
Studies of risk-modifying factors on health defined geographically or temporally
31
Case control study
Two groups with different outcomes are compared on the basis of a causal attribute
32
Meta analysis
Contrast and combine results of multiple studies to identify patterns Difficulties: differences in data collection + differing criteria Requires careful data extraction, manipulation and assessment
33
Aetiological studies
Provide info on risk factor and causes of a condition | Can only prove correlation
34
Diagnostic studies
Shows specificity and sensitivity of a diagnostic test
35
Prognostic studies
Provide info on outcome and morbidities of patients after exposure
36
Therapeutic studies
Provide info on effectiveness of treatment
37
Pros and cons of prospective data collection
Follows patients who share a characteristic Pros: less missing data, reliable info Cons: time consuming, large amount of data to analyse
38
Pros and cons of retrospective data collection
Pros: immediately available data Cons: no control of variables, often missing data
39
How can you identify confounding variables?
Draw a directed acyclic graph to show causative relationships
40
Describe linear modelling
``` Uses parsimony (prefers the simplest explanation) Mean part = the relationship Residual part = unexplained and error (normally distributed) Have to adjust results to account for effects of confounding variables and competing exposures ```
41
PECOS
``` Patient Exposure Comparison Outcome Study design ```
42
Controlled vocab search
Medline uses MeSH - medical subject headings
43
Principles of critical appraisal
``` Is research: Relevant Robust Objective Important ```
44
How is research robust?
Good design, no bias: Sampling bias - random sampling, multi site Measurement bias - info bias, observer bias, recall bias? Analytical bias - loss to follow up, omitted variables? Dissemination bias - publication bias?
45
How is research important?
If there is good quality of design (no of patients) and good strength of evidence
46
What is required for effectiveness of evidence?
``` Controlled trials Randomisation Concealment and masking Low drop out and intention-to-treat Sufficient statistical power ```
47
Describe a critical appraisal of a prognostic study
Routinely collected Bespoke measurements Ignore studies with >80% LTFU (lost to follow up) Compare baseline data of LTFU with non LTFU Conduct sensitivity analysis
48
Describe a critical appraisal of a diagnostic study
What is sensitivity and specificity of test? What is predictive value of positive and negative test result?
49
Sensitivity
Ability of test to pick up true positives
50
Specificity
Ability of test to avoid false positives
51
What is external validity?
Appropriate spectrum of patients - participants must have same range of severity, symptoms and prevalence of condition as target population
52
What are the key issues with evidence from an aetiological study?
External validity of participants Exposures/ outcomes measured blind Follow up - was sufficient time left for outcome to occur? Loss to follow up - assess potential differential bias

RESS (11 decks)

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