Table 3

Levels of certainty regarding net benefit

Level of certaintyDescription
HighThe available evidence usually includes consistent results from well-designed, well-conducted studies in representative primary care populations. The studies assess the effects of the treatment, test or other intervention on treatment or other relevant outcomes. The conclusion is therefore, unlikely to be strongly affected by the results of future studies.
ModerateThe available evidence is sufficient to determine the effects of the intervention on outcomes, but confidence in the estimate is constrained by such factors as:

  • The number, size, or quality of individual studies;

  • Inconsistency of findings across individual studies;

  • Limited generalizability of findings to routine primary care practice;

  • High likelihood of bias;

  • Lack of coherence in the chain of evidence.


As more information becomes available, the magnitude or direction of the observed effect could change, and that change may be large enough to alter the conclusion.
LowThe available evidence is insufficient to assess effects on treatment and other outcomes of interest.
Evidence is insufficient because of:

  • The limited number or size of studies;

  • Important flaws in study design or methods;

  • Inconsistency of findings across individual studies;

  • Gaps in the chain of evidence;

  • High likelihood of bias;

  • Findings not generalizable to routine primary care practice;

  • Lack of information on important outcome measures. More information may allow estimation of effects on treatment outcomes.