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