Horses for courses Flashcards
What is bias?
Systematic error that distorts results and leads to wrong conclusions. It exists in all studys at any phase of research.
What is cross sectional studies?
Descriptive/analytic. Provides snapshot of population through survey that can measures prevalence.
Why are cross sectional studies important?
Informing about prevalence of disease and 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.
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 and cross sectional
What is a cohort study?
Can be retrospective or prospective and uses odds ratio. Compares exposed group with control group to see any health outcomes.
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 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 the benefits of cohort studies?
Reduces survival bias and recall bias.
Good for long development time disease
Good for incidence
What are case-control studies?
Retrospective and uses relative risk. Compares diseased and healthy group to study exposure.
What are the strengths of case control studies?
Efficient in time and money and effective in long term study of diseases, especially rare diseases. 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 type of study is a randomised control trial?
Experimental epidemiology- intervention to establish effectiveness and confirm hypotheses about causal relationships
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.
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 for RCT?
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
What are the types of observational studies?
Descriptive and analytical
What is a case report?
A description of a single individual patient case. It is cheap and easy however it lacks temporality and there may be seleciton bias.
What is a case series?
A collection of multiple case reports. It is cheap and easy and useful for rare diseases. However, it lacks temporality (long term tracking) and there may be selection bias.
