Evidence based dentistry

Question 1

systematic review

Answer 1

type of literature review that uses systematic methods to identify, appraise and synthesize all relevant studies on a topic.

Question 2

benefits of systematic reviews

Answer 2

provide reliable unbiased evidence
save readers time
identify gaps where good studies not available
resolve inconsistencies
limit bias and improved accuracy

Question 3

5 key characteristics of a systematic review

Answer 3

• well formulated question (PICO)
• comprehensive data search (multiple databases, multiple languages, published and unpublished)
• unbiased selection and abstraction process (done by at least 2 reviewers, clear reasons for exclusion)
• assessment of papers (how well studies have been designed and conducted, assess risk of bias)
• synthesis of data (pooling)

Question 4

what structure can be used to help develop a well formulated question for a systematic review

Answer 4

PICO
population
intervention
comparison
outcomes

Question 5

7 step process of systematic review

Answer 5

1. authors - 2 or more, topic expert and methodological expert
2. study protocol - in advance of review
3. specific question - using PICO
4. search strategy - comprehensive and repeatable, multiple databases, published and unpublished, no language restrictions
5. specific inclusion/ exclusion criteria (agreed in advance)
6. critical appraisal - assessing risk of bias in each paper, quality assessment
7. synthesis - pooling of data

Question 6

2 quality assessment tools that may be used when assessing papers

Answer 6

composite scales - numerical value given to individual factors to give an overall estimate of quality
component approach - assess relevant methodological aspects individually (preferred)

Question 7

meta analysis

Answer 7

optional part of systematic review
process of using statistical methods to combine the results of different studies

Question 8

what does the vertical line represent in forest plots

Answer 8

line of no difference between intervention and control

(0 if differences, 1 if ratios)

Question 9

dichotomous vs continuous data

Answer 9

dichotomous - illness or not, death or not, odds ratio, risk ration (binary data)
continuous - blood pressure, weight etc

Question 10

what shape is given to pooled analysis on a forest plot

Answer 10

diamond

Question 11

what are the 3 types of heterogeneity

Answer 11

clinical - variations in participants, interventions, study design etc
methodological - variation in methods used
statistical - excessive variation in results

Question 12

how may statistical heterogeneity appear on a forest plot

Answer 12

poor overlap of confidence intervals

Question 13

what test can be used to assess heterogeneity and what result would demonstrate significantly significant heterogeneity

Answer 13

chi-squared test
P<0.1 indicates statistically significant heterogeneity

Question 14

what I^2 statistic would indicate heterogeneity

Answer 14

> 50%

Question 15

fixed vs random effects

Answer 15

fixed - assumes that the studies brought together are almost identical - assumes true answer for each study is the same
random - assumes studies are slightly different (results in wider confidence intervals)

Question 16

what method does cochrane use to assess quality of meta analysis

Answer 16

GRADE

Question 17

5 factors that can lower quality of meta analysis (GRADE)

Answer 17

• high or unclear risk of bias
• inconsistency between studies (possible heterogeneity)
• indirectness (were all studies investigating the same thing)
• imprecision (wide confidence intervals)
• publication bias (negative/ null results not published)

Question 18

what should bias assessment look at in RCTs (3)

Answer 18

sequence generation (method of randomisation)
allocation concealment
blinding of participants and assessors

Question 19

when is dichotomous used and when is continuous data used

Answer 19

continuous - weighted and standardised mean differences

dichotomous - odds and risk ratios, risk reductions, NNT