A systematic review of observational studies uses the GRADE framework to rate the quality of evidence. Observational studies start at which initial evidence level, and which factor can UPGRADE that rating?
- A High; dose-response gradient
- B Moderate; large study size
- C Low; dose-response gradient ✓
- D Very low; absence of publication bias
Correct answer: C. Low; dose-response gradient
Explanation
In the GRADE framework, observational studies start at LOW quality of evidence (RCTs start at HIGH). Evidence can be upgraded from low to moderate or high if: there is a very large effect size (RR >2 or <0.5), a dose-response gradient exists, or all plausible confounding would only reduce the effect. Large sample size alone does not upgrade GRADE ratings. Absence of publication bias avoids downgrading but does not upgrade.
Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.
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