descriptive epidemiology

Question 1

literature review

Answer 1

has two main approaches
narrative
and systematic

Question 2

narrative review

Answer 2

brings together published literature into a single article to allow readers to understand issues
aka literature review,scoping review or non systematic review

Question 3

systematic review

Answer 3

highly structured approach to search and sift and summarising literature

Question 4

narrative reviews stregnths and weakness

Answer 4

easier and faster to write
more up to date
useful when looking at areas of limited research
can be usefuk when work from different disciplines is being bought together in an easily answerable research question

disadvantage
subject to bias as authors select work to support their opinion
no search is specified

Question 5

systematic reviews

Answer 5

aim to collate all evidence that relates to a highly focused research question
highly specified protocol
includes evidence based on pre specified data (inclusion criteria)
can take many months to design the search

disadvantages
a less comprehensive search strategy may mean you miss out on evidence
only as good as indices used
only as good as evidence incorprated
very quickly out of date due to delay in publishing,look at search date not publication date
published every 2-10 years

Question 6

method of systematic review

Answer 6

research quesrion
structured search
indices
screening
reporting
writing
submitting

Question 7

structured search

Answer 7

combine searches together

Question 8

indices

Answer 8

medlline
mbase
psychinfo
need to explain which indices you will use
based on published research

Question 9

registeries

Answer 9

registration of research yet to be completed
important to avoid duplication or ommision

Question 10

screening

Answer 10

PRISMA diagram
shows how many articles have been found or removed due to indices being the same
how many articles will be involved

Question 11

grey information

Answer 11

many implementations and programmes have been reported but with varying degrees of accuracy
eg on google scholar

Question 12

meta analysis

Answer 12

a quantitative formal epidemiological study desgin used to systematically assess previous research studies to derive conclusions about that body of research

combines quatitatve findings from separate studies into a pooled estimate

Question 13

forest plot

Answer 13

used in meta analysis
contains
study
intervention and control
relative risk
diamond is a combination of all the relative risks
if confidence interval crosses 0 we cant reject the null hypothesis

Question 14

heterogeneity

Answer 14

variation in a studies outcome
clinical-within patients and selection criteria
methodological- study designs blinding etc
statistical;reporting differences

Question 15

weight

Answer 15

usually proportional to study size
fixed and random effects models may give you different weights

Question 16

funnel plot

Answer 16

shows balance of evidence between studies assuming an overall side effect
more publications on one side of the line may mean that the studies havent been reported

Question 17

implications of meta analysis

Answer 17

limited by quality of studies used
will need a systematic review
may need to go back to original authors to ask for more data

Question 18

two types of efficacy endpoints

Answer 18

Primary endpoint – this is the endpoint for which the study has been powered; that is to say that the number of trial participants (sample size) will have been recruited on the basis of the pre-specified power and difference.
Secondary endpoint – it is common that a study will want to examine a slightly different endpoint in addition to the primary endpoint. For example, while a study seeks to examine survival (i.e. alive or dead) another – often ‘softer’ - measure such as recurrence of disease or hospital admission might also be measured. If the secondary endpoint is proven but the primary endpoint is not, then the findings of the study may still contribute to the understanding of disease.

Question 19

safety endpoints

Answer 19

Safety endpoints are quite intuitive. On the one hand it could be anaphylaxis or direct mortality associated with the therapy. Such major issues should usually be detected early in the trial process (before its rolled out to large numbers of patients). But more commonly the safety endpoints will be more nuanced: potentially measuring commonly observed adverse events (AEs) and grading them into a hierarchy of significance. A large proportion of patients reporting AEs will require investigation.

Question 20

composite endpoint

Answer 20

can describe any endpoint
multiole potential endpoints have been added together

Question 21

surival analysis

Answer 21

use kaplan meier plots

Question 22

bradford hill cirteria

Answer 22

strength-a stronger association increases the confidence that an exposure causes an outcome
consistency-consistent findings rule out errors that might occur in studies
specificity-a disease arising among specific workers is valuable in supporting argument for casuality but concedes lack of specificty doesnt invalidate casual relationship
temporality-an exposure must precede an outcome
biological gradient-theres a dose response relationship between exposure and outcome
plausibility-relationship shouldnt be implausible
coherance-ensures that association is in line with existing science
experiment-not ethical
analogy-rests on exsisting knowledge

Question 23

internal validity

Answer 23

an association exists in an experiment
the extent to which findings accurately describe the relationship between exposure and outcome in the context of the study

Question 24

external validity

Answer 24

findings from an experiment can be generalised to other people

Question 25

selection bias

Answer 25

when a person has been exposed or had the outcome
eg healthy worker effect/non response bias

Question 26

how to avoid selection bias

Answer 26

minimise non response
control representative of target population
compare respondents with non respondants

Question 27

information bias

Answer 27

misclassification of exposure or disease status or both
includes recall,response,interviewer and diagnostic bias

Question 28

interviewer bias

Answer 28

more likely to ask patient questions is they have the outcome about the expposure

Question 29

recall bias

Answer 29

pt may forget past exposures

Question 30

non differential missclassification

Answer 30

when exposure status is misclassified between everyone
odds ratio will always be towards null (differntia can be towards either)

Question 31

confounding

Answer 31

the effect of the extraneous variable that wholly or partially accounts for the apparent effect of the study,exposure or that masks an underlying true association

Question 32

criteria for confounding

Answer 32

1.knowledge about subject matter
2.3 conditions-its assocaited with the exposure in the source population,associated with the outcome in the absence of the exposure,not a consequence of exposure
3.stratification:look at difference of apparent affect within different population strata
4.compare crude and adjusted estimates

Question 33

effect modification

Answer 33

when the strength of an association varies over different levels of a third variable eg gender

natural phenomenon
present stratified results eg by gender

Question 34

test for effect modification

Answer 34

breslow day test
q test
interaction terms in regression models

Question 35

synergism and antagonism

Answer 35

synergism is where the effect modifier potentiates the effect of the exposure

antagonism is where the effect modifier dimishes the effect of the exposure

Question 36

crude vs adjusted model

Answer 36

Crude model (which is the univariate analysis of exposure vs outcome). This is simply looking at the impact of the exposure on the outcome – with no consideration of anything else.
Adjusted model (which is the multivariate analysis of a range of exposures vs. outcome). A multivariate analysis means that multiple potential exposures have been included. The inference is that the outputs of these analyses mean that holding all other adjusted variables equal, X is the association between exposure and outcome.