Table 1

Grading of recommendations and evidence.

Grading of recommendations

A
Supported by at least two level I investigations
B
Supported by one level I investigation
C
Supported by level II investigations only
D
Supported by at least one level III investigation
E
Supported by level IV and V evidence

Grading of evidence

I
Large randomized trials with clear-cut results; low risk of false-positive (alpha) error or false-negative (beta) error
II
Small randomized trials with uncertain results; moderate-to-high risk of false-positive (alpha) error and/or false-negative (beta) error
III
Nonrandomized, contemporaneous controls
IV
Nonrandomized, historical controls and expert opinion
V
Case series, uncontrolled studies, and expert opinion

Vincent et al. Critical Care 2006 10:R120   doi:10.1186/cc5026