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Question 627
Clinical Management → Clinical Practice
Classification
Question
SSBAQuestion Header
Evidence-based medicine
Question Stem
A guideline group is grading evidence for a clinical recommendation. Which source represents Level 1a evidence in the hierarchy described?
Options
A
A systematic review of randomised controlled trials including meta-analysis
B
An individual randomised controlled trial with a narrow confidence interval
C
A systematic review of cohort studies
D
An individual case-control study
E
Expert opinion
Explanation
Level 1a evidence is a systematic review of randomised controlled trials including meta-analysis and carries grade A recommendation. An individual RCT with a narrow confidence interval is Level 1b; a systematic review of cohort studies is Level 2a; an individual case-control study is Level 3b; and expert opinion is Level 5.
Option Validity
B) An individual randomised controlled trial with a narrow confidence interval is Level 1b, not Level 1a.
C) A systematic review of cohort studies is Level 2a, not Level 1a.
D) An individual case-control study is Level 3b, not Level 1a.
E) Expert opinion is Level 5, the lowest evidence level listed.
Further Reading
Saxena MRCOG-1 Basic Sciences — Principles of Clinical Practice, printed p. 1.