Study Designs for Healthcare Questions Flashcards
What is EBM a combination of?
- Individual clinical expertise
- Best external evidence
- Patient values and expectations
Stages of AAAA framework
- Assess
- Access
- Appraise
- Act
Categories of healthcare questions
- Frequency (how common/who gets it)
- Aetiology (what causes it)
- Prognosis (what happens to those who have it)
- Effectiveness (are there any treatments/do treatments have side effects)
- Diagnosis (how do we find if someone has it)
- Patient experience (what is the patient’s experience of the condition)
Study designs for each healthcare question
- Frequency = ecological, cross-sectional
- Aetiology = case-control, cohort
- Effectiveness = RCT
- Diagnosis = special cross-sectional, test accuracy study
- Patient experience = qualitative research
Characteristics of descriptive studies
- Observational
- About frequency and pattern of disease
- Used for hypothesis generation
- Often precede analytical studies
Types of descriptive study
- Case report/case series
- Cross-sectional study
- Ecological study
What is a case report/case series?
CR = detailed report of unusual condition or occurrence in a single patient
- CS = detailed report of unusual ‘condition’ or ‘occurrence’ in several patients
What is a cross-sectional study?
Study where information is collected in a planned way from individuals in a defined population at one point in time
What is an ecological study?
Study where information is collected from a whole population to compare disease frequencies
Characteristics of analytical studies
- Comparison of 2 or more groups
- Establish whether an exposure causes an outcome
Categories within analytical studies
- Observational
- Interventional/experimental
Observation vs interventional analytical study
- O = researcher is observer of exposure + outcome
- I = researcher allocates exposure + observes outcome
Types of analytic observational studies
- Case control
- Cohort
What is a case control study?
- Starts with identification of outcome (eg. disease)
- Subjects grouped according to outcome (cases and controls)
- Level of “exposure” to one or more factors measured and compared
What is a cohort study?
- Starts with identification of exposure (eg. risk factor)
- Subjects grouped according to exposure or no exposure
- Groups followed up over time and amount of diseases developing is compared
Characteristics of a case control study (how many exposures it captures, how many outcomes it measures, how long between exposure and development of outcome)
- Can investigate multiple exposures
- Only investigates 1 outcome
- Do not have to wait for outcome
Characteristics of a cohort study (how many exposures it captures, how many outcomes it measures, how long between exposure and development of outcome)
- Only investigates 1 exposure
- Can investigate multiple outcomes
- Have to wait for outcome to occur
What is a controlled clinical trial?
Experimental study where researchers decide whether participants receive new intervention or a control treatment
What do controlled clinical trials investigate
Effectiveness of intervention
How do randomised controlled clinical trials (RCTs) reduce bias?
Use random allocation of treatments (like flipping a coin)
Pre-requisite for an RCT
- Genuine uncertainty about which treatment is best
- New treatment will do more good than harm
Hierarchy of evidence from different types of study (best to worst)
- RCT
- Cohort study
- Case control study
- Case series/case report
- Expert opinion (“anecdotal” evidence)
