Wk2- how much evidence is needed Flashcards
types of clinical questions
intervention- effectiveness of treatment
diagnostic- diagnostic tests, or presence/absence of signs and symptoms
prognostic- asking about the future
patient experiences/concerns- qualitative research to understand the why and how
what is “just in case” information
information that is pushed out to you. usually when you’re not needed the information
just in time information
creating a question and filtering through results to acquire information
steps to creating an answerable question 4
- identify a knowledge gap/ information need
- classify the need for information as either intervention, diagnostic, prognostic or patients experience/concern.
- clearly articulate required components from the PICO framework.
- review question, seek feedback from others and refine work
comparison in PICO is not used it what kind of questions?
prognostic
qualitative research
inductive reasoning, where we move from specific –> general. focuses on the how and why of peoples actions
quantitative research
deductive reasoning, general –> specific. typically the more reliable data, numerical.
hierarchies of evidence
quality of evidence improves from the bottom to top
bottom areas, unfiltered information
top areas, filtered information
list the hierarchy of evidence pyramid worst to best (7)
systematic reviews
critically appraised topics
critically appraised articles
RCT
cohort study
case control study
background information/ expert opinion
level 1 evidence (best evidence) for intervention, diagnosis and prognosis?
a systemic review of level 2 studies
i: systematic review of RCT
d: systematic review of a study of test accuracy with
- an indecent blinded comparison
- a valid reference standard
-and defined clinical presentation
p: systematic review of a prospective cohort study
level 2 evidence for intervention?
randomized controlled trial
level 2 evidence for diagnosis
a study of test accuracy with an indecent blinded comparison. with a valid reference standard, amount consecutive persons with a defined clinical presentation
level 2 evidence for prognosis
prospective cohort study
list the hierarchies of studies strongest to weakest 6
- randomized controlled trial (experimental) - analytical
- cohort study (observational) - analytical
- case-control study “ -analytical
- cross sectional study “ -descriptive
- ecological study “ -descriptive
- case reports/series “ -descriptive
case report/case series
-observational studies
-descriptive
-no comparison group
-no assigned exposure
report: description of a single patient/presentation that is unusual
series: combines multiple cases (people)
lower end of pyramid because its subject to opinion and bias
what area of the study should you look at to identify what type of study design it is?
methods section
cross-sectional study
-analytic or descriptive
-observational
-no assigned exposures
-comparison group
-obtain exposure and outcome data at the same time
-single point time snapshot (present)
advantages of cross sectional studies 6
-quick and easy
-no follow up
-disease prevalence information at a specific time
-may suggest associations between outcome and exposure
-useful for public health planning/understanding -and for hypothesizes generation
disadvantages of cross-sectional studies 4
-doesn’t tell us cause or effect
-it is only a snapshot of time
-potential for confounding
-cannot determine incidence
ecological studies
-analytic or descriptive
-compares exposure across populations/groups not individuals
-observational
-no assigned exposure
ecological fallacy is what
error made when information about groups of people is used to make inferences about individuals
cohort study
-observational
-analytical
-comparison group
-exposure first then outcome
-prospective or retrospective
-follow up
-incidence of the outcome in the exposed group is compared to the incidence of the outcome in the group who were not
prospective cohort study and an example
compares something different between groups in present time and the changes/differences in the future
example:
groups receiving an income supplement and groups that aren’t. where do they end up in the future?
retrospective cohort study
look at an exposure group and non exposure group from the past and see if they reach outcome
advantages of cohort studies 6
- ethical rct replacement
-can examine multiple outcomes
-association between exposure and disease
-measures disease incidence in both groups
-good for prognostic studies
disadvantages of cohort studies 3
-prospective can be lengthy and costly
-reterospective: cheaper and easier but potential issues with bias (recall) and need a good record
-consideration of confounding
case control studies
-observational
-analytic
-compare 2 groups, one with the outcome of interest (case) and another without (control)
-retrospective
-compare exposure history
-outcome first work back to find the exposure
case control studies works in what time frames?
research in reverse.
present subjects with or without outcome and look back to see which risk factors have been exposed to
advantages of case control studies 6
-quick and inexpensive
-suitable for rare disease
-possible to evaluate large number of potential causes/risk factors
-better for researching causality than cross sectional studies
-good where there is a long latency period
disadvantages of case control studies 7
-association, not causation
-requires representation samples of cases and controls
-selection of appropriate controls can be difficult
-not suitable for rare exposures
-can only study one outcome
-selection and recall bias
-cannot calculate prevalence or incidence
difference between case control study and cohort
cohort studies always start with exposure/cause and arrives at outcome
cause/ exposure: smoker/non smoker - outcome: cancer/no cancer
case control always starts with the outcome then arrives at exposure/cause
outcome: cancer/no cancer - cause/exposure: smoker / non smoker
randomized controlled trial
-special type of cohort study
-examines cause- effect relationship between predictor and outcome variables
-at least two groups involved (experimental group and control group)
-randomisation ensures groups are similar as possible at start of stud
-experimental, intervened on.
-from present -different groups are exposed to different things and followed for outcomes
-prospective
advantages of RCT
-gold standard in establishing cause and effect
-suitable to study more than one intervention
disadvantages of RCT 3
-epensive/time consuming
-ethically complex
-hard to use info in real life due to the level of control
flowchart of study designs
