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 quality of evidence, the balance between desirable effects and undesirable ones, the values and preferences, and the resources and costs.
   • Grade 1 recommendations are meant to identify practices where benefit clearly outweighs risk. These recommendations can be made by clinicians and accepted by patients with a high degree of confidence.
   • Grade 2 recommendations are weaker and are made when the benefits and risks are more closely matched and are more dependent on specific clinical scenarios. In general, physician and patient preference plays a more important role in the decision making process in these circumstances.
2. An evaluation of the level of evidence (A to C) based on the level of evidence to support the recommendation is noted.
   • 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.