Table 2 Key to evidence statements and grading recommendations defined by SIV.*

   A. Good evidence for efficacy and substantial clinical benefit support recommendation for use.

   B. Moderate evidence for efficacy or only limited clinical benefit supports recommendation for use.

   C. Evidence for efficacy is conflicting and does not allow supporting a recommendation for or against use, but recommendations may be made on other grounds.

   D. Moderate evidence for lack of efficacy or for adverse outcome supports a recommendation against use.

   E. Good evidence for lack of efficacy or for adverse outcome supports a recommendation against use.

   I. There is insufficient evidence (in quality and quantity) to make a recommendation; however, other factors may influence decision-making.

Quality of Evidence

   I. Evidence from at least 1 randomized, controlled trial.

   II. Evidence from at least 1 clinical trial without randomization, from cohort or case-controlled analytic studies (preferably from more than 1 centre) or from multiple time-series studies or dramatic results from uncontrolled experiments.

   III. Evidence from opinions of respected authorities based on clinical experience, descriptive studies, or reports of expert committees.