A systematic review of the literature was undertaken comparing proton pump inhibitors with H2- receptor blockers for the prevention of gastro-intestinal bleeding in ICU patients.
The following figure was included:
- a) Name the type of graph illustrated in the above figure. (10% marks)
- b) What does it show? (25% marks)
- c) What are the benefits of this type of analysis? (25% marks)
- d) What are the disadvantages of this analysis? (40% marks)
Answer and interpretation
a) Name the type of graph illustrated in the above figure. (10% marks)
- Forest plot
b) What does it show? (25% marks)
- Combining the trials together, PPI use results in an odds ratio of 0.35 or reduction in the risk of bleeding compared to H2RA. Alternatively, PPI use results in 65% reduction (1- 0.35) in bleeding.
c) What are the benefits of this type of analysis? (25% marks)
- Combines small studies with limited power, increasing the number and thus the ability to pick up a positive effect. Small studies with low power (due to small effect, small numbers) run the risk of a Type II error.
d) What are the disadvantages of this analysis? (40% marks)
- Individual studies might have different patient populations (with different risk of bleeding) or different definitions of outcome.
- Individual studies might have been conducted with different degrees of rigour (blinding, etc.)
- There is publication bias to positive studies so that negative studies are not reported.
- Need full disclosure how the studies were selected, their scientific grading, subgroup analyses and assessment of heterogeneity.
- Pass rate: 83%
- Highest mark: 8.0
- Candidates who scored well showed an in-depth understanding of the applied physiology and consequences of the various therapeutic options. Candidates who scored poorly omitted key points.