Definitions Flashcards
Pros and Cons of RCT
Advantages:
1) RCTs are considered to be the most reliable form of scientific evidence in the hierarchy of evidence that influences healthcare policy and practice
2) Reduce selection bias
3) Reduce allocation and performance bias if blinded
4) Reduced detection bias if double-blind
5) Allows direct comparison, and if balanced accounts for confounding variables
6) Reduced spurious causality
Grade B (if single) or Grade A (if multiple evidence)
Disadvantages
1) Limitations of external validity (inclusion/exclusion making trial pop not the same as real world)
2) Time
3) Costs
4) Conflict of interest dangers (pharma sponsorship)
5) Ethics ( it may be difficult to test this ethically in an RCT if it becomes ‘obvious’ that the control subjects have poorer outcomes)
Advantages and disadvantages of prospective cohort studies
Advantages
1) Temporal sequence, allows temporality to be established
2) Good for studying rare exposures if cohort selection considered carefully
3) Can examine multiple effects from a single exposure
4) Limits selection bias if cohort selected carefully
5) Allows measurement of potential confounding variables if foreseen
Disadvantages
1) Need large number of subjects
2) Long time duration
3) Expensive and timely
4) Not good for studying rare disease
5) Not good for studying diseases with long latency i.e. duration from exposure to development of disease
6) Differential loss to follow up can introduce bias
7) Not good for acute disease i.e. the common cold
Advantages and disadvantages of retrospective cohort studies
Advantages
1) Temporal sequence, allows temporality to be established
2) Good for studying rare exposures if cohort selection considered carefully
3) Can examine multiple effects from a single exposure
4) Limits selection bias if cohort selected carefully
Disadvantages
1) Need large number of subjects
2) Not good for studying rare disease
3) Differential loss to follow up can introduce bias
4) Use of records not intended for research i.e. clinical records, results in low quality data collection
5) Missing data common
6) Data needed to adjust for confounding variables often. missing
Advantages and disadvantages of case-control studies
Advantages
1) Efficient for studying rare disease
2) Efficient at studying disease with long latency periods
3) Quicker
4) Cost less money
5) Advantageous when exposure data is expensive or hard to obtain.
6) They are advantageous when studying dynamic populations in which follow-up is difficult
Disadvantages
1) Selection bias
2) Sometimes difficult to find relevant controls
3) Information on exposure is subject to observation bias
4) Recall bias
5) Don’t allow calculation of risk or incidence
Advantages and disadvantages of cross-sectional studies
Advantages
1) Less time-consuming than case-control or cohort studies
Inexpensive
2) Good, quick picture of prevalence of exposure and prevalence of outcome
Disadvantages
1) Difficult to determine temporal relationship between exposure and outcome (lacks time element)
2) May have excess prevalence from long duration cases (such as cases that last longer than usual but may not be serious)
Advantages and disadvantages of ecological studies
Advantages
1) Inexpensive
2) Less time-consuming
3) Simple and easy to understand
4) Examines community-, group-, or national-level data and trends
Disadvantages
1) Subject to the ecological fallacy, which infers association at the population level whereas one may not exist at the individual level
2) Difficult to detect complicated exposure-outcome relationships
Categories of Audit (5)
1) Financial audit
2) Operational audit
3) Departmental review
4) Standards based audit: comparison of care against set of standards
- Important in medicine and clinical governance
5) Systems based audit: evaluation of processes occurring within an institution
- Most common in clinical governance
Pillars of clinical governance
Patient & Public involvement
Information systems & IT
Research and development
Audit
Training & Education
Clinical effectiveness
Definition of composite outcome
Composite outcomes, in which multiple end points are combined, are frequently used as primary outcome measures in randomized trials and are often associated with increased statistical efficiency.
Justification of composite outcome
1) The individual components of the composite are clinically meaningful and of similar importance to the patient.8
2) The expected effects on each component are similar, based on biological plausibility- which is in the end the rationale for using a composite endpoint)
3) Accordingly, regulatory guidelines also require components for which it can be assumed treatment will beneficially influence in a similar way.
4) The clinically more important components of composite endpoints should at least not be affected negatively.11
Definition of pearson’s product-moment correlation coefficient
Measure of the strength and direction of association that exists between two variables measured on at least an interval scale
Requirements:
- normally distributed data
- two variables are structurally independent
- -> one variable should not be forced to vary with another
- only one pair of measurements per participant
Definition of regression
Regression: allows one variable to be predicted from another
Factorial design
Factorial design: permits investigation of the effects (both separately and combined) of more than one independent variable on a given outcome
e.g. 2x2 comparison
Pros and cons of factorial design
Assessment of an array of effects on an outcome
Pros:
- Allows multiple comparisons to be made without having to increase the number of people recruited
- -> as long as the number required meets power calculation for least difference comparison, continue to add comparison won’t change power
Cons:
- Interpretation difficult
- Assumes non-synergistic effect
- Unable to provide head-to-head comparison
