Grades of recommendation for antithrombotic agents.

The strength of any recommendation depends on two factors: the trade-off between benefits and risks, and the strength of the methodology that leads us to estimates of the treatment effect. The framework that we used for this conference captures these factors. We grade the trade-off between benefits and risks in two categories: (1) the trade-off is clear enough that most patients, despite differences in values, would make the same choice; and (2) the trade-off is less clear, and each patient's values will likely lead to different choices. We grade methodologic strength in three categories: (1) randomized trials, ideally summarized in a meta-analysis, that show consistent results; (2) randomized trials with inconsistent results; and (3)observational studies. The framework summarized in Table 1 therefore generates recommendations from the very strong (1A: benefit/risk clear, methods strong) to the very weak (2C: benefit/risk questionable, methods weak). Whatever the grade of recommendation, clinicians must bring their judgment considering local and individual patient circumstances, and patient values, to bear in making individual decisions. In general, however, they should place progressively greater weight on expert recommendations as they move from 2C to 1A.