Quality of evidence and classification of recommendations
| Quality of evidence | |
| I | Evidence obtained from at least one randomised controlled trial |
| II-1 | Evidence obtained from well designed controlled trials without randomisation |
| II-2 | Evidence obtained from well designed cohort or case-control study |
| II-3 | Evidence obtained from comparison between time and places, with or without intervention |
| III | Opinion of respected authorities, based on clinical experience and expert committees |
| Classification of recommendations | |
| A | There is good evidence to support the statement |
| B | There is fair evidence to support the statement |
| C | There is poor evidence to support the statement but recommendation made on other grounds |
| D | There is fair evidence to refute the statement |
| E | There is good evidence to refute the statement |