Applying Classification of Recommendations and Lev
Estimate of Certainty (precision) of Treatment Effect
Size of Treatment Effect
CLASS I
Benefit >>> Risk
Procedure/Treatment
SHOULD be performed/
administered
CLASS IIa
Benefit >> Risk
Additional studies with
focused objectives needed
IT IS REASONABLE
to perform procedure/
administer treatment
LEVEL A
Multiple populations
evaluateda
▪Recommendation that
procedure or treatment is
useful/effective
▪Recommendation in favor of
treatment or procedure being
useful/effective
Data derived from multiple
randomized clinical trials or
meta-analyses
LEVEL B
Limited populations
evaluateda
▪Sufficient evidence from
multiple randomized trials or
meta-analyses
▪Recommendation that
procedure or treatment is
useful/effective
▪Some conflicting evidence
from multiple randomized trials
or meta-analyses
▪Recommendation in favor of
treatment or procedure being
useful/effective
Data derived from a
single randomized trial or
nonrandomized studies
LEVEL C
Very limited populations
evaluateda
Only consensus opinion
of experts, case studies, or
standards of care
▪Evidence from single
randomized trial or
nonrandomized studies
▪Recommendation that
procedure or treatment is
useful/effective
▪Some conflicting evidence
from single randomized trial or
nonrandomized studies
▪Recommendation in favor of
treatment or procedure being
useful/effective
▪Only expert opinion, case
studies, or standard of care
▪Only diverging expert opinion,
case studies, or standard of care
Suggested phrases for writing should
recommendations
is recommended
is indicated
is useful/effective/beneficial
is reasonable
can be useful/effective/beneficial
is probably recommended or
indicated
Comparative effectiveness
phrasesb
treatment/strategy A is probably
recommended/indicated in
preference to treatment B
it is reasonable to choose treatment
A over treatment B
treatment/strategy A is
recommended/indicated in
preference to treatment B
treatment A should be chosen
over treatment B
A recommendation with Level of Evidence B or C does not imply that the recommendation is weak. Many
important clinical questions addressed in the guidelines do not lend themselves to clinical trials. Although
randomized trials are unavailable, there may be a very clear clinical consensus that a particular test or therapy
is useful or effective.
