Study Designs for Healthcare Questions

Question 1

What is EBM a combination of?

Answer 1

• Individual clinical expertise
• Best external evidence
• Patient values and expectations

Question 2

Stages of AAAA framework

Answer 2

• Assess
• Access
• Appraise
• Act

Question 3

Categories of healthcare questions

Answer 3

• 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)

Question 4

Study designs for each healthcare question

Answer 4

• Frequency = ecological, cross-sectional
• Aetiology = case-control, cohort
• Effectiveness = RCT
• Diagnosis = special cross-sectional, test accuracy study
• Patient experience = qualitative research

Question 5

Characteristics of descriptive studies

Answer 5

• Observational
• About frequency and pattern of disease
• Used for hypothesis generation
• Often precede analytical studies

Question 6

Types of descriptive study

Answer 6

• Case report/case series
• Cross-sectional study
• Ecological study

Question 7

What is a case report/case series?

Answer 7

CR = detailed report of unusual condition or occurrence in a single patient
- CS = detailed report of unusual ‘condition’ or ‘occurrence’ in several patients

Question 8

What is a cross-sectional study?

Answer 8

Study where information is collected in a planned way from individuals in a defined population at one point in time

Question 9

What is an ecological study?

Answer 9

Study where information is collected from a whole population to compare disease frequencies

Question 10

Characteristics of analytical studies

Answer 10

• Comparison of 2 or more groups
• Establish whether an exposure causes an outcome

Question 11

Categories within analytical studies

Answer 11

• Observational
• Interventional/experimental

Question 12

Observation vs interventional analytical study

Answer 12

• O = researcher is observer of exposure + outcome
• I = researcher allocates exposure + observes outcome

Question 13

Types of analytic observational studies

Answer 13

• Case control
• Cohort

Question 14

What is a case control study?

Answer 14

• 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

Question 15

What is a cohort study?

Answer 15

• 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

Question 16

Characteristics of a case control study (how many exposures it captures, how many outcomes it measures, how long between exposure and development of outcome)

Answer 16

• Can investigate multiple exposures
• Only investigates 1 outcome
• Do not have to wait for outcome

Question 17

Characteristics of a cohort study (how many exposures it captures, how many outcomes it measures, how long between exposure and development of outcome)

Answer 17

• Only investigates 1 exposure
• Can investigate multiple outcomes
• Have to wait for outcome to occur

Question 18

What is a controlled clinical trial?

Answer 18

Experimental study where researchers decide whether participants receive new intervention or a control treatment

Question 19

What do controlled clinical trials investigate

Answer 19

Effectiveness of intervention

Question 20

How do randomised controlled clinical trials (RCTs) reduce bias?

Answer 20

Use random allocation of treatments (like flipping a coin)

Question 21

Pre-requisite for an RCT

Answer 21

• Genuine uncertainty about which treatment is best
• New treatment will do more good than harm

Question 22

Hierarchy of evidence from different types of study (best to worst)

Answer 22

• RCT
• Cohort study
• Case control study
• Case series/case report
• Expert opinion (“anecdotal” evidence)