evidence based medicine Flashcards
what is evidence based medicine?
conscientious use of current best evidence in making decisions about care of individual patients
what is quantitative research?
Involves the structured collection of data that is numeric or can be transformed into numeric measures. Ideally evaluated using statistical analysis
answers - is this effective? by how much?
what is qualitative research?
Involves the systematic collection, organization, description and interpretation of textual, verbal or visual data.
answers questions - ‘how’, ‘why’ and ‘in what way?’
- cannot confirm relationships between variables or causality - often used to generate qauntatitive
what are some challenges for evidence based medicine?
- research quality
- keeping up with new findings
(main ones - more in notes but irrelevant i think??)
what is the dependant and independent variable?
dependent variable or health outcome = what is being measured e.g. improved health & wellbeing, diagnosis, disease onset, treatment response
independent variable = exposure or treatment which is manipulated in some (measurable) way
what is reliability meaning?
research methods can reproduce the same results multiple times
factors must be consistent: time, investigator changes, measurement tool changes
what is validity meaning?
requires the variables of interest to be defined, the theory or knowledge base for the research design and/or questions is credible, and research methods are comprehensive and appropriate to research scope
how is validity ensured for qualitative research?
Cross-check analysis of focus group discussions for plausibility and coherence by comparing critical reasoning and interpretation against underpinning theory and results from other studies
how is validity ensured for quantitative research?
Evaluation of a treatment regime will exactly define the independent variable under investigation and how much it will be manipulated, the conditions under which the dependent variable is measured (e.g. instrument/tool used, frequency of measurements)
how is validity ensured for a survey?
Pilot test question wording and response options for comprehensibility and comprehensiveness on small number of individuals who are representative of the respondent groups of interest
what is the hierarchy of evidence pyramid - state from bottom to top
bottom = least reliable
top = most reliable
editorials, expert opinion
case series, case reports
case-control studies
cohort studies
randomised control trials
systematic reviews & meta analyses
what are the factors that contribute to higher rankings in hierarchy of evidence?
- replicability (transparency, generalisability)
- sample size/statistical power
- controlling/accounting for effects of other variables
- research designs that reduce risk of biases
what is the general concept of systematic review process?
lots of different studies are analysed and combined to form systematic review
- involves secondary analysis of primary research data
it must have: clearly defined research objectives & explicitly described, systematic & therefore reproducible methods
what should fully be described in randomised control trial protocol?
PICO (S)
Population = people included (and excluded)
Intervention = experimental treatment or exposure
Control/comparator = may be placebo, no treatment/exposure, routine practice, best practice
Outcome = measures need to be relevant & accurate
Study design
what role does ethics have in randomised control trial?
ethical review is essential as you’re choosing to not treat some individuals so you have to way up benefits and harm, also MUST have informed consent
what reporting standards are randomised control trials based on?
consort
- scottish medicines consortium & NICE then make recommendations for prescribing after trial
what are considered gold standard method to assess efficacy of treatment or demonstrate causal relationship?
randomised control trials
what is randomisation in RCT’s (randomised control trials) ?
Random allocation to intervention or control
good because…
- gives likely balance of all factors affecting outcome
- Facilitates blind objective unbiased assessment of outcome
what are the phases of drug development?(for trials)
phase 1 - safety, dose-finding, volunteers
phase 2 - safety, how effective, how often?
phase 3 - efficacy, safety
phase 4 - post approval in large population
what are potential limitations of RTC’s?
- Poor recruitment
- Generalisability (does recruitment reflect real world populations and settings?)
- Ethics committee approval required
- Double blinding not always possible (e.g surgery vs. chemotherapy).
- Sensitivity to loss of respondents (e.g. death, drop out (>20% or significant differences in experimental and control group numbers likely to be problematic to interpretation and reliability) though beware not always a detriment to publication!
what is the meaning of risk in EBM context?
probability or likelihood of a health outcome of interest (likelihood of an event or outcome)
- can be used to estimate the probability of negative/adverse AND positive/successful outcomes (it encompasses both positive and negative outcomes)
- it’s integral to making informed decisions about medical interventions.
how do you calculate absolute risk?
number of new cases of disease in at risk population during specified time period DIVIDED BY total number of individuals in at risk population during same time period
(simplified = in specific time period, in an at risk area - n.o new people with disease/total number of people)
how do you calculate relative risk?
absolute risk for all individuals exposed to risk factor during specified time period DIVIDED BY absolute risk for all individuals not exposed to risk factor during same time period
(people who got it who were exposed to risk/people who got it who weren’t exposed to risk)
what are the outcomes of case-control study expressed as?
RR = relative risk
and
OR= odds ratio
how do you calculate OR?
odds of disease in population exposed to risk factor DIVIDED BY odds of disease in population not exposed to a risk factor
what is relative risk?
measure of the strength of association between an exposure and an outcome in a cohort or prospective study.
what is odds ratio?
frequently used in case-control studies (while RR is used in cohort studies)
- used to estimate the strength of association between exposure & outcome
what does it mean if
(A) OR and RR close to 1
(B) OR and RR greater than 1
(C) OR and RR less than 1
(A) indicates no difference in probability/likelihood
(B) increased probability that health outcome of interest will occur when exposure to variable
(C) reduced probability that health outcome of interest will occur in cases exposed to variable undre investigation
