Understanding Research Evidence Flashcards
What type of evidence do we look for?
Peer-reviewed publications and/or systematic reviews.
Study design (PICO) must be relevant for what is being looked for. Authors sometimes incorrectly define their designs
Consider possible study limitations and bias
Statistical power
What is a randomised controlled trial?
An experimental study (not observational) where peoeple are randomly allocated.
What are the types of observational studies?
If there is no comparison group it is a descriptive study.
If there is a comparison group:
If exposure -> outcome it is a cohort study (eg what has eating apples done to people)
If outcome ->exposure it is a case control study (what is causing these strokes?)
If exposure and outcome are at the same time it is a cross-sectional study
What are the benefits of conducting a randomised controlled trial?
The gold standard in clinical research
Designed specifically to minimise bias
Is the equivalent of a controlled experiment in basic science
If properly designed it can be free of bias and thus statistically robust
What is a randomised controlled trial?
Participants are randomized into 2 or more groups and each group receives a different intervention.
Assignment of treatment occurs “by chance”
Participants and staff both don’t know what they are giving the patient, the treatment or the placebo.
What research questions can be addressed by a randomised controlled trial?
Interventional questions; is the treatment effective? Is treatment A more or less effective than treatment B?
What are the disadvantages of conducting a randomised controlled trial?
While it has internal validity, having exclusion and inclusion criteria may mean it doesn’t work for people outside this cohort.
Sometimes, can’t be done due to ethical concerns
Can be expensive
How is bias eliminated in an RCT?
Blinding of participants and staff
Placebo controlled
What is the difference between passive and active placebo?
Passive placebo - mimics administration only
Active placebo - mimics side effects of intervention
What is a cohort study?
An observational study where participants are followed over time (Eg effect of birthweight on future development of heart disease)
Participants with specific characteristics are a “cohort”
Differences between them are measured and they are followed over time.
What are cohort studies used for?
Determining risk factors/predictors of risk
Aetiology (What causes the outcomes?)
Prognosis (What happens in this disease over time?)
Diagnosis (If test x is positive, what happens to the patient?)
What are the pros and cons to cohort studies?
Pros: Best way to identify incidence and relative risk of a disease
Usually a clear view of the exposure-outcome timeline
Can investigate multiple outcomes
Useful to study rare exposures
Cons: Assessing rare events or events that take a long time to develop may be too slow to yield results
Selection bias - hard to match exposure and non-exposure groups exactly
Not a great design for rare diseases
Loss to follow-up can lead to bias (hard to follow everyone in the cohort due to random reasons)
Exposure status might change over time
What is a case-control study?
Observational study comparing 2 matched groups of participants; 1 has the outcome, the other doesn’t. The study analyses the differences and identifies risk factors
What questions can case-control studies answer?
Risks
Diagnosis
Prognosis
What are the pros and cons of case-control studies?
Pros: Most-widely used study design
Simplest to execute
Quick to perform
Cheap
Cons:
More susceptible to bias
Easy to do but can be done incorrectly
How is the control group for a case-control study selected?
Control group should be free of the outcome
Represent individuals selected as cases
Selection of the controls MUST be independent of the exposure
What are cross-sectional studies?
Measure a population at a particular point in time in order to detect a particular outcome
What questions can cross-sectional studies answer?
Frequency - how common is the outcome?
Aetiology - What risk factors are associated with the outcome
Diagnosis - Does the new tst perform as well as the current standard test?
What information can’t cross-sectional studies provide us with?
Can’t determine relationship between outcome and exposure
All that can be said is that at a particular point in time obese people had a higher prevalence of arthritis but we can’t make a definitive relationship between arthritis and obesity.
What are qualitative studies?
Name given to group of designs which focus on patient oriented outcomes
Qualitiative studies are very systematic in their approach but they also ask questions like:
Why do people….
What are the reasons for…
How do people feel about….
They use interviews, focus groups, and participant observation.
What type of strategies are used for qualitative studies?
Involve explicit sampling strategies and systematic data analysis
Portray the voice of the participant, usually absent from qualitative studies and therefore provides complementary information
What is the value of qualitative studies if they are so subjective in nature?
There is value in understanding personal experience and how it impacts the patient and practitioner experience
These methods can bridge the gap between scientific evidence and clinical practive and provide additional improvements to patient care.
What kinds of problems can qualitative studies help solve?
Patient compliance/adherence with medication
Disparities between how doctors and patients view medical conditions and treatments
What is a case study or case-series study?
A study describing a patient or small group of patients affected by a specific disease or exposed to a factor
