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