Grid for determining the grade of recommendations
| Grade of recommendation | Number of SLRs and/or high-level or medium-level studies |
| A | One high-level SLR or five or more consistent high-level studies |
| B | Four high-level studies |
| C | Three high-level studies or one high-level and two medium-level studies |
| D | Two or less high-level studies, or inconsistent or inconclusive studies of any level |
SLR, systematic literature review.