Table 2.

NHLBI Grading of the Strength of Recommendations

Grade	Strength of Recommendation*
A	Strong recommendation
	There is high certainty based on evidence that the net benefit† is substantial.
B	Moderate recommendation
	There is moderate certainty based on evidence that the net benefit is moderate to substantial, or there is high certainty that the net benefit is moderate.
C	Weak recommendation
	There is at least moderate certainty based on evidence that there is a small net benefit.
D	Recommendation against
	There is at least moderate certainty based on evidence that there is no net benefit or that risks/harms outweigh benefits.
E	Expert opinion (“There is insufficient evidence or evidence is unclear or conflicting, but this is what the Work Group recommends.”)
	Net benefit is unclear. Balance of benefits and harms cannot be determined because of no evidence, insufficient evidence, unclear evidence, or conflicting evidence, but the Work Group thought it was important to provide clinical guidance and make a recommendation. Further research is recommended in this area.
N	No recommendation for or against (“There is insufficient evidence or evidence is unclear or conflicting.”)
	Net benefit is unclear. Balance of benefits and harms cannot be determined because of no evidence, insufficient evidence, unclear evidence, or conflicting evidence, and the Work Group thought no recommendation should be made. Further research is recommended in this area.

^*In most cases, the strength of the recommendation should be closely aligned with the quality of the evidence; however, under some circumstances, there may be valid reasons for making recommendations that are not closely aligned with the quality of the evidence (eg, strong recommendation when the evidence quality is moderate, such as smoking cessation to reduce CVD risk or ordering an ECG as part of the initial diagnostic work-up for a patient presenting with possible MI). Those situations should be limited and the rationale explained clearly by the Work Group.

^†Net benefit is defined as benefits minus risks/harms of the service/intervention.

CVD indicates cardiovascular disease; ECG, electrocardiogram; MI, myocardial infarction; and NHLBI, National Heart, Lung, and Blood Institute.