According to this system, there are two components to any treatment recommendation:

1. Designation of the strength of the recommendation (strong: 1; or weak: 2) based on the degree of confidence that the recommendation will provide more benefit than harm;
   • Grade 1 recommendations are those in which the benefits of an intervention clearly outweigh its risk and burdens. All well-informed patients would choose such a treatment, and the physician can securely recommend it without a detailed knowledge of the underlying data.
   • Grade 2 recommendations are weaker and reflect therapies where the benefits and risks are uncertain or are more closely balanced. For such interventions, patients may choose different options based on their underlying values.

We have adopted the language of "recommending" the use of strong Grade 1 guidelines and "suggesting" the use of weaker Grade 2 guidelines.

2. An evaluation of the level of evidence (A to C) based on the confidence that the estimate of effect is correct.
   • Grade A, or high-quality evidence,usually comes from well-executed randomized trials yielding consistent results, and occasionally, obs ervational studies with large effects.
   • Grade B, or moderate-quality evidence, comes from randomized clinical trials with important limitations, inconsistent randomized trials, and strong observational studies.
   • Grade C, or low or very low quality evidence, includes flawed randomized trials and most observational studies as well as data from case reports, descriptive studies, and expert opinion.