Evidence Based Dentistry

Question 1

What is critical appraisal?

Answer 1

process of assessing and interpreting evidence through the systematic consideration of its validity, relevance and results

Question 2

What is CASP?

Answer 2

• Critical Appraisal Skills Programme

Question 3

What issues are considered during critical appraisal?

Answer 3

• are the results of the trial valid?
  
  • focussed question
    - PICO
  • conduct of study
    - randomisation
    - blinding
    - allocation
    - concealment
• what are the results?
  
  • effect of treatment
    - what has been measures?
    - what direction?
    - how large?
  • precision
• are the results relevant to clinical practice
  
  • generalisable
  • clinically important to outcome measures
  • adverse effects/harm

Question 4

What is PICO

Answer 4

• Population, patient or problem
  
  • being studied
• Intervention or exposure
  
  • being considered
• Comparison intervention or exposure
  
  • if applicable
• Outcome of interest

Question 5

How does the way a study was conducted affect its validity?

Answer 5

• assignment of treatment to patient should be randomised
• all patients who entered the trial must be accounted for
• patients, health workers and study personnel must be blind
• groups must be similar at the start of the trial
• apart from the intervention, group must be treated equally

Question 6

What are randomised controlled trials?

Answer 6

• RCT/Clinical Trial
  
  • gold standard study design
  • effectiveness and efficacy
  • useful for clinical studies
• provide strongest evidence on effectiveness of treatments
• inclusion/exclusion criteria applied to population
  
  • randomisation and separation into two groups
  • experimental treatment
  • comparator or placebo
• four design elements
  
  • specification of participants
  • control/comparison groups
  • randomisation
  • blinding/masking
• disadvantages:
  
  • if non-blinded can overestimate treatment effects
  • difficult to design and construct
    - ethical issues
    - feasibility
    - costs
  • risk of bias
  • generalisability often limited

Question 7

What is absolute risk difference?

Answer 7

• difference in risk between groups
• 0 is the valve of no difference

Question 8

What are confidence intervals?

Answer 8

• the range of values the absolute risk difference will take in the population

Question 9

What is the number needed to treat?

Answer 9

• number of patients needed to treat to prevent one patient from developing disease/condition/outcome

Question 10

What is risk ratio?

Answer 10

• relative measure of risk to control
  
  • how many times more likely in test group than control
• 1 is the value of no difference

Question 11

What are case report/case series?

Answer 11

• report on a single patient or series of patients
  
  • outcome of interest
  • no control group involved
• used for:
  
  • identifying new disease outcome
  • hypothesis generation
• disadvantages
  
  • cannot demonstrate valid statistical associations
  • lack of control group

Question 12

What are cross sectional studies?

Answer 12

• observation of a defined population at a single point in time
  
  • exposure and outcome determined at the same time
• used for:
  
  • estimating prevalence of a disease
  • investigating potential risk factors
• disadvantages
  
  • causality
  • confounding
  • recall bias

Question 13

What are cohort studies?

Answer 13

• establish a group in a population and measure exposures
  
  • follow up over period of time
  • identify those that develop disease
    - outcome of interest
• used for:
  
  • estimating incidence of disease
  • investigating cases of disease
  • determining prognosis
  • timing and direction of events
• disadvantages:
  
  • controls difficult to identify
  • confounding
  • blinding difficult
  • large samples needed, not good for rare diseases
  • expensive and time consuming