Chapter 14: Key Approaches Flashcards
What is an experimental study?
-researcher intervenes to change exposure then observes/measures what happens (Cause-Effect)
What is an observational study?
- researcher observes/measures exposure and outcome (does not manipulate)
- environment is not changed
- not a “true” experiment
- associations
What are the two types of observational studies?
- descriptive
- analytical
What are descriptive studies?
- help identify patterns and generate hypothesis
- case report, surveys, fact-finding inquiries
- frequency and distribution of single variables
What are analytical studies?
- groups are being compared
- aims to associate exposure/intervention and outcome
What are case reports?
- An in-depth analysis of a single individual, unit, or event
- Direct observation and questioning
- Provide considerable detail
- Usually concern rare events
What are the challenges of case reports?
A) difficult to draw clear causal linkages;
B) generalizability of findings;
C) potential for observer bias
What are the three types of analytical studies?
- Cohort (prospective)
- Case-Control
- Cross-Sectional
What is the goal of cohort (prospective studies)?
- characterize (observe) exposures in participants and then track them over time
- compare exposed vs. controls
What is the goal of case-control studies?
- enroll participants with disease or outcome and find matched controls
- compare previous exposures between groups
What is the goal of cross-sectional studies?
- enroll participants and measure exposures and health simultaneously
- snapshot
Explain cohort studies and provide pros and cons
- Longitudinal or prospective
- Start with an exposure and then follow group overtime; compare between exposed and un-exposed
- E.g., Nurses Health Study
- Pros: can match subjects at baseline; establish timing of events; can standardize exposures
- Cons: associative study (not causal); blinding is difficult; not randomized; rare diseases need large sample size and long follow-up
Explain case-control studies and provide pros and cons
- Retrospective (opposite of cohort)
- Start with an outcome/disease and then work backwards to identify possible causes
- Pros: relatively quick and cheap; most feasible for rare disorders or outcomes with long latency period; fewer subjects needed than other studies
- Cons: associative study (not causal); reliance on recall and records to determine exposures (past diet??); not randomized; control groups hard to find; selection bias
Explain cross sectional studies and provide pros and cons
- Study at one point in time to determine if there is an association between exposure and health
- Pros: relatively cheap and simple
- Cons: associative study (not causal); recall bias problems; confounders may be unequally distributed
What is the STROBE Checklist?
Strengthening The Reporting of Observational studies in Epidemiology
What are the two types of experimental studies?
- Randomized controlled trial
- Non-randomized controlled trial
Explain Randomized Clinical Trial (RCT) and provide pros and cons
- Normally used to test new drugs and treatments
- Participants who meet inclusion criteria are randomly allocated to either receive treatment or not, and then followed over time
- Random allocation is completely blinded (to participant, researcher)
- Pros: unbiased distribution of potential confounders; blinding; statistically robust
- Cons: expensive (time, $); volunteer bias; ethical concerns
What is CONSORT?
• Consolidated Standards of Reporting Trials
• Evidence-based, minimum set of
recommendations for reporting randomized trials
• 25-point checklist
What are quasi-experiments?
- Between cohort and RCT
- Intervention exists but not planned before starting research, and thus random allocation not involved
- Researcher will assign treatment based on a criteria (e.g., cost, feasibility, convenience, cut-off score) and not randomly
- Subject to concerns over internal validity (control and exposed groups may not be comparable at baseline)
What are Systematic review & Meta-analyses?
Collects all studies on a topic and statistically combines results
What is Randomized-controlled trial?
Randomly selects group of people to receive treatment and another to get placebo
What is Non-randomized (quasi) experiment?
Non-randomly assigns groups of people into treatments
What is a cohort study?
Follows a group of people over time
What is a case control study?
Compares group of people with condition vs. people without
What is a cross-sectional study?
Assess exposure-outcome at one point in time in a group
On the evidence pyramid, what type of research is in the bottom and what type of research is close to the tip of the triangle?
bottom - observational studies
top - experimental studies
What are the observational studies included in the evidence pyramid in order from the bottom to top?
- in vitro research
- animal research
- editorial, opinions, ideas
- case reports
- case series
- case control studies
- cohort studies
What are the experimental studies included in the evidence pyramid in order from the bottom to top?
- RCT
- Systematic review
- Meta-analysis
What are the Bradford Hill Criteria for Causation in order?
- Strength (effect size)
- Consistency – is it reproducible
- Specificity – specific population, specific site, etc.
- Temporality – cause and then effect
- Biological gradient – greater exposure = greater incidence
- Plausibility – a believable mechanism linking
- Coherence – epid and lab studies
- Experiment
