Science of EBM Flashcards
(30 cards)
What are the primary research study types?
- observational studies (case control/cohort/cross-sectional studies)
- experimental studies (randomised/non-randomised trials)
What are the secondary research types?
- reviews:
- expert opinion
- systematic review
- meta-analysis
What is a case study/series/report?
A report on a series of patients with an outcome of interest
What are the advantages of a case study/series/report?
- quick and cheap to conduct
- rapid publication
- early indicators of problems
- can help detect new drug side effects and potential uses (adverse/beneficial)
What are the disadvantages of a case study/series/report?
- statistically weak
- no control group
- very small numbers of patients
- cases may not be generalisable to wider population
What is a cross-sectional study?
The observation of a defined population at a single point in time or time interval. Exposure and outcome are determined simultaneously
What are the advantages of a cross-sectional study?
- cheap and simple
- ethically safe
- useful for planning purposes
What are the disadvantages of a cross-sectional study?
- cannot determine which is cause and which is effect
- volunteer bias
- unequal distribution of confounders
What are the different complications that can happen during a clinical study?
- confounders: uncontrolled external variables
- spurious association (when 2 variables are associated but not causative of each other)
What is a case-control study?
Researchers choose people with a particular result (the cases) and interview the groups or check their records to ascertain what different experiences they had. They compare the odds of having an experience with the outcome to the odds of having an experience without the outcome
What are the advantages of a case-control study?
- simultaneously look at multiple risk factors
- good at studying rare conditions or diseases for long latent period
- useful as initial studies to establish an association
- do not require a long follow up period
What are the disadvantages of a case-control study?
- retrospective study that relies on patient recall to determine exposure or patient records
- confounders
- selection of control group is difficult
- unlikely to detect rare causes of disease
What is a cohort study?
A clinical research study in which people who presently have a certain condition or receive a particular treatment are followed over time and compared with another group of people who are not affected by the condition to compare outcomes
What are the advantages of a cohort study?
- ethically safe
- subjects can be matched
- can show cause precedes the effect
- easier and cheaper than a RCT
What are the disadvantages of a cohort study?
- high drop out rate- follow up must be as complete as possible
- exposure may be linked to hidden confounder
- blinding can be difficult
- outcome of interest may take longer time to occur
What is a randomised control trial?
A controlled clinical trial that randomly (by chance) assigns participants to two or more groups, do a follow up of outcomes and compare.
What are the different design modifiers of RCTs?
- single blind: subjects do not know which treatment they are getting
- double blind: subjects nor investigators know which treatment the subjects are getting
- crossover: each subject received both the intervention and control treatment randomly, separated by wash-out period
- placebo controlled: control subjects receive placebo
What are the advantages of RCTs?
- unbiased distribution of confounders
- clearly identified populations
- randomisation helps statistical analysis
- more likely to be blinded
What are the disadvantages of RCTs?
- expensive (time and money)
- volunteer bias (population may not be representative)
- ethical issues if treatment group response badly/better than expected
What are the different comparison methods of clinical research?
- parallel group comparison: each group receives a different treatment and the groups are compared
- paired comparison: subjects are matched to balance confounders like age and sex and the differences between subject pairs are analysed
- within subject comparison: subjects are assessed before and after intervention and analysis is done within subject changes
What are the potential problems associated with RCTs?
- impossible: with treatments for rare diseases where the number of patients are too limited
- unecessary: when treatment produces dramatic effect
- stopping trials early: interim analysis to assess whether treatment is showing benefit and can be stopped early
- resources: substantial money/time/enery
- generalisability: often carried out on specific patients over short period of time
Describe how you would assess cause and effect?
- is the association due to a chance occurence?
- is it due to a flaw in the methodology? (bias)
- is it due to another factor linked to both the exposure and the outcome? (confounder)
What are the advantages and disadvantages of expert review?
advantages:
- comprehensive survey
- answers a specific question
disadvantages:
- expert bias
What is a systematic review?
A summary of the clinical literature. A systematic review is a critical assessment and evaluation of all research studies that address a particular clinical issue. The researchers use an organized method of locating, assembling, and evaluating a body of literature on a particular topic using a set of specific criteria. A systematic review typically includes a description of the findings of the collection of research studies
