Table 2.

Classification of the evidence

Colour code	Standardized statement	Situations included
1. White	Unknown effect: Insufficient published research on the intervention’s effect on the outcome.	No RCTs, one low quality RCT with any result, or
		One moderate-to-high quality RCT where 95% CI of the RR includes 1, or
		Only narrative reporting
2. Grey	Unknown effect: Inconclusive published research on the intervention’s effect on the outcome.	At least two RCTs, 95% CI of the point estimate for a relative risk crosses widely on both sides of 1 (ranges from < 0.5 to > 2)
3. Green	Positive effect: The intervention likely reduces the risk of the adverse outcome.	At least two moderate-to-high quality RCTs included in a meta-analysis or IPD analysis, 95% CI of the point estimate of the RR is entirely below 1
4. Yellow	Possible positive effect: The intervention may reduce the risk of the adverse outcome.	At least two RCTs included in a meta-analysis or IPD analysis, 95% CI of the point estimate of the RR is entirely below 1, but there is concern about the quality of the data, or
		at least two moderate-to-high quality RCTs included in a meta-analysis or IPD analysis, 95% CI of the point estimate of the RR includes 1 but 90% CI of the point estimate of the RR is entirely below 1, or
		One moderate-to-high quality RCT, 95% CI of the point estimate of the RR is entirely below 1
5. Red	No positive effect: The intervention is not likely to reduce the risk of the adverse outcome.	Other situations, including meta-analysis results suggestive of harm