Cohort vs case-control studies
Cohort: Measure exposure status, Follow over time, Compare development of outcome (incidence)
Case control: Identify people with outcome, Find people without outcome, Compare exposure likelihood beforehand (odds)
Case control studie
Is the exposure more or less likely in people with the outcome (cases) than without (controls)?
Do case control studies use incidence or odds? Why
Odds, Can’t calculate incidence of outcome, Have selected number of people in study with and without outcome
What’s odds ratio?
Odds Ratio (OR) = (a/c) / (b/d)
Odds of exposure in cases = a/c
Odds of exposure in controls = b/d
Interpreting odds ratio vs Relative Risk (RR)
Relative risks and odds ratios with rare diseases
When disease is rare, OR approximates the RR (rare disease assumption)
Can interpret OR just like RR
Use RR interpretation in this course
During case control studies you measure someone when they have an outcome, when do you measure a control group.
You pick a control group from population at the same date and time as you find someone with the outcome and measure em both
When choosing the control person of a case control study, what do you need to make sure of ?
Need to represent the odds of exposure in people without the outcome in the source population
Must be capable of becoming a case eg if study is on prostate cancer, you need to choose a control who has prostate
What is randomized controlled trials (RCT)
experiment that compares two or more groups to determine if a treatment or intervention is effective by randomly assigning participants to an experimental group (receiving the intervention) or a control group (receiving a placebo, standard treatment, or no treatment)
What makes RTC different to studies
Interventional vs observational
Studies:researchers don’t intervene, they just compare.
RCT: The researcher actively gives an intervention (drug, therapy, program).
Strongest design for testing cause-and-effect because randomization reduces bias.
what is a cofounder
confounding occurs when the relationship between an exposure and an outcome is distorted by a third variable, known as a confounder.
What is Randomisation/
random allocation in studies and why do you do it.
Equal chance for each
participant to be in either group. this means if population big enough, should have same proportion of
confounder in each group
Examples to ensure trial stays random
Large numbers, Concealment of
allocation, Intention-to-treat analysis
what is commonly used in control group of Randomised controlled trials
Placebo
Explain Concealment of Allocation
a method in randomized controlled trials (RCTs) that hides the upcoming treatment assignments from researchers and participants to prevent selection bias. to ensure groups involve no bias
Cohort vs
Randomised controlled trials
Cohort: Ascertain exposure status,
then find out outcome(s)
RCT: Randomly assign exposure
status, then find out
outcome(s)
In terms of ethics, what was the The Milgram Obedience Studies
experiments
examining whether people would act
against their conscience if instructed by
an authority figure. They found out they would as prepared to obey even if it
meant causing serious injury and distress
to another person
What needs to be considered for research to be acceptable
- Assess the benefits and harms and ensure the ratio is acceptable
- Be aware of potential vulnerabilities of participants
- Avoid or manage conflicts of interest (eg can’t influence for pay)
- Obtain informed consent from participants
5.Consider how the benefits and burdens of the research should be shared across
society
‘Beneficence’ and ‘Non-Maleficence’
Beneficence: we have to ‘benefit’
others. In research it is the obligation to ensure that the research is generating something of value that justifies the costs
Non maleficence: not to harm others without a justifying reason. either taking steps to avoid these harms or ensuring that the benefits are sufficient to justify the harms
what is Clinical Equipoise
there must be genuine uncertainty within the expert medical community about the relative merits of treatments in different arms of a clinical trial. Eg once the data suggests a negative impact you can’t keep the participant going.
What is Conflicts of Interest
Where there is secondary gain. Eg Financial ties: A researcher is funded by or owns stock in the company whose product they are testing.
What does Empowering (and not exploiting)
participants who may be vulnerable refer to when proposing a study
exploitation means getting someone to do a study if they are disadvantaged eg paying someone who struggles financially or someone who is ill educated
What is informed consent and what does the consent form need to include
Participant needs to be AWARE of purpose, risks, and processes of the study, and consent must be in writing
