Table 1.
Categorization of evidences and recommendations of the clinical guidelines1
| Oxford system level of evidences2 | |
| 1A | Systematic review of randomized clinical trials |
| 1B | Individual RCTs with narrow confidence intervals |
| 1C | All or none studies |
| 2A | Systematic reviews of cohort studies |
| 2B | Individual cohort study including low-quality RCTs |
| 2C | Outcomes research; ecological studies |
| 3A | Systematic review of case-control studies |
| 3B | Individual case-control studies |
| 4 | Case series and poor-quality cohort and case-control studies |
| 5 | Expert opinion without explicit critical appraisal or descriptive epidemiology |
| GRADE system3 | |
| Quality of evidence criteria | |
| High | (1) Further research is unlikely to change confidence in the estimate of the clinical effect. |
| Moderate | (2) Further research may change confidence in the estimate of the clinical effect. |
| Low | (3) Further research is very likely to impact confidence on the estimate of clinical effect. |
| Strength of recommendation criteria | |
| Strong | (1) Factors influencing the strength of the recommendation included the quality of the evidence, presumed patient-important outcomes, and cost. |
| Weak | (2) Variability in preferences and values, or more uncertainty. Recommendation is made with less certainty, higher cost, or resource consumption. |
| NCCN categories of evidence and consensuses4 | |
| Category 1 | Based upon high-level evidence, there is uniform NCCN consensus that the intervention is appropriate. |
| Category 2A | Based upon lower-level evidence, there is uniform NCCN consensus that the intervention is appropriate. |
| Category 2B | Based upon lower-level evidence, there is uniform NCCN consensus that the intervention is appropriate. |
| Category 3 | Based upon any level of evidence, there is major NCCN disagreement that the intervention is appropriate. |
1Most clinical guidelines used their simplified adaptation of Oxford and GRADE system; above are selected examples.
2
Data from clinical guidelines by Canadian Association for the Study of the Liver.
3
Data from clinical guidelines by Korean Liver Cancer Study Group.
4
Data from the NCCN formal website (Available from: https://www.nccn.org/professionals/physician_gls/categories_of_consensus.aspx). RCT: Randomized controlled trials; NCCN: National Comprehensive Cancer Network.