What are the chances of that happening 2 Flashcards
What is an outcome?
Disease
What is an outcome?
Disease
What is bias?
Systematic error that distorts results and leads to wrong conclusions. It exists in all studies at any phase of research.
What is cross sectional studies?
Descriptive study that measures of prevalence of health characteristics of a population a given time which assesses the burden of disease or health needs of a population.
Why are cross sectional studies important?
Informing how to plan and allocate health resources
What kind of study is a cross sectional study?
Both descriptive and analytical to identify correlations between exposure and outcomes.
How are cross sectional studies conducted?
Surveys in order to collect data about prevalence.
What are the benefits of cross sectional studies?
Cheap and easy to conduct. It is ethically safe and can measure prevalence for all factors under investigation. It is good for generating hypotheses and descriptive analysis. Data on variables
What are the weaknesses of cross sectional studies?
It measures correlation but it is difficult to determine cause-effect relationships. Cannot estimate incidence and susceptible to bias due to recall and selection bias. It is not suitable to study rare diseases with a short duration.
What is selection bias?
Participants are systematically different in their characteristics compared with eligible non-participants
What is analytic epidemiology?
Quantifies the association between exposures and outcomes to test hypotheses about casual relationship.
What are observational studies?
No intervention by investigator. It is an analysis of spontaneously occurring events It is used to explore aetiology (cause)
What are the types of Observational studies?
Cohort and case-control.
What is a cohort study?
Compare the outcomes of health following exposure with a control group. This allows for direct calculation of incidence, using relative risk.
What is a cohort study most beneficial for?
Diseases with a long development time.
What is case-control?
Compare the exposures once deciding on an outcome.
How are cohort diseases framed?
Formulated using a question which covers population (such as children), exposure (such as a disease) and outcome (such as mortality.)
What are the benefits of cohort studies?
Natural history and incidence of disease, especially the rare exposures. It is good for investigating diseases with a long development time and we can calculate incidence, relative risk and confidence intervals with this study. It reduces survivor bias. Minimal recall bias.
What is attrition bias?
Systematic difference between people who leave the study and those who continue.
What is the weaknesses of cohort study?
Costly and time-consuming due to long-follow up periods which can lead to attrition bias. It is susceptible to selection bias.
What are case-control studies?
Determine association between an outcome and exposure. It is an observational study where groups are defined by outcome and it is retrospective.
How are case-control studies formulated?
Questions have a framework of population, exposure, comparison and outcome.
What are the strengths of case control studies?
Efficient in time and money and effective in long term study of diseases, especially rare diseases. Allows us to calculate useful estimates and study multiple risk factors at once.
What are the weaknesses of case control studies?
Difficult to choose an appropriate control group and can become inefficient if frequency of exposure is low.
What is experimental epidemiology?
Exposure and intervention to establish effectiveness and confirm hypotheses about causal relationships
What type of study is a randomised control trial?
Experimental epidemiology
What is a RCT?
Clinical trial to compare outcomes after participants receive an intervention. Best evidence and every participant has an equal chance of being selected.
How is an RCT formulated?
Questions with population, intervention, comparator and outcome. Eg. In comparison to usual care, is prenatal counselling effective in reducing pre-eclampsiain women diagnosed with Lupus?
What are the benefits of RCTs?
Establish causation, minimises bias, publishable and comparative.
What are the weaknesses of RCT?
Expensive, logistically challenging. Results may not reflect reality. It has ethical limitations where informed consent does not occur, and the context of randomised patients with different backgrounds and support.
How to mitigate bias?
Use pre-existing records, not select people based on outcome, consistently account for the study population, and using double blind or allocation concealment. To mitigate attrition bias using appropriate analyses such as intention
