Table 2.
Methods used to assess the quality of evidence to support the recommendations
| Guideline 1, 2006 Evidence Grading System | |
| A. Primary Reports of New Data Collection: | |
| Class A: Randomized, controlled trial | |
| Class B: Cohort study | |
| Class C: Non-randomized trial with concurrent or historical controls, Case-control study, Study of sensitivity and specificity of a diagnostic test, Population-based descriptive study | |
| Class D: Cross-sectional study, Case series, Case report | |
| B. Reports that Synthesize or Reflect upon Collections of Primary Reports: | |
| Class M: Meta-analysis, Systematic review, Decision analysis, Cost-effectiveness analysis | |
| Class R: Consensus statement, Consensus report, Narrative review | |
| Class X: Medical opinion | |
| Guideline 2, 2006 LEVELS OF EVIDENCE | |
| 1 one systematic review (A1 quality; see below) or at least two independent studies of A2 quality; | |
| 2 at least two independent studies of B quality | |
| 3 one study of A2 or B quality, or several studies of C quality; | |
| 4 expert opinion, e.g. that of members of the Guideline Committee | |
| Quality levels (intervention and prevention) | |
| A1 Systematic reviews including at least some studies of A2 quality, with results consistent across individual studies. | |
| A2 Randomized comparative clinical trial (RCT) of sound methodological quality (randomized double-blind controlled trial) of sufficient size and consistency. | |
| B Randomized comparative clinical trial (RCT) of moderate quality or insufficient size; other comparative study (non-randomized comparative cohort study or case-control study). | |
| C Non-comparative study. | |
| D Expert opinion, e.g. that of members of the Guideline Committee. | |
| Guideline 3, 2009 none said | |
| Guideline 4, 2011 none said | |
| Guideline 5, 2012 Classification of methodological quality of individual studies | |
| A1 Systematic review of at least two independently conducted studies of A2 level | |
| A2 Randomised double-blind comparative clinical research of good quality of sufficient size Research relative to a reference test (a ‘golden standard’) with predefined cut-off points and independent assessment of the results of a test and golden standard, on a sufficiently large series of consecutive patients who all have had the index and reference test Prospective cohort study of sufficient size and follow-up, at which adequately controlled for ‘confounding’ and selective follow-up sufficient is excluded. | |
| B Comparative research, but not with all the features as mentioned under A2 (this includes patient–control research, cohort study) Research relative to a reference test, but not with all the attributes that are listed under A2 Prospective cohort study, but not with all the features as mentioned under A2 or retrospective cohort study or patient-monitoring research | |
| C Not comparative research | |
| D Opinion of experts | |
| Conclusions based on | |
| 1 Research of level A1 or at least two examinations of level A2 performed independently of each other, with consistent results | |
| 2 One examination of level A2 or at least two examinations of level B, performed independently of each other | |
| 3 One examination of level B or C | |
| 4 Opinion of experts | |
| Guideline 6, 2013 | |
| The taxonomy includes ratings of A, B, or C for the strength of recommendation for a body of evidence. A being consistent and good quality patient-oriented evidence. B being inconsistent and limited quality patient-oriented evidence. C based on consensus, usual practice, opinion, disease-oriented or case series for studies of diagnosis, treatment, prevention, or screening. They recommendations were graded according to the Strength of Recommendation Taxonomy | |
| Guideline 7, 2013 LEVELS OF EVIDENCE | |
| I Evidence obtained from high-quality diagnostic studies, prospective studies, or randomized controlled trials | |
| II Evidence obtained from lesser-quality diagnostic studies, prospective studies, or randomized controlled trials (e.g., weaker diagnostic criteria and reference standards, improper, randomization, no blinding, less than 80% follow-up) | |
| III Case-control studies or retrospective studies | |
| IV Case series | |
| V Expert opinion | |
| GRADES OF RECOMMENDATION BASED ON STRENGTH OF EVIDENCE | |
| A Strong evidence A preponderance of level I and/or level II studies support the recommendation. This must include at least 1 level I study | |
| B Moderate evidence. A single high-quality randomized controlled trial or a preponderance of level II studies support the recommendation | |
| C Weak evidence A single level II study or a preponderance of level III and IV studies,s including statements of consensus by content experts, support the recommendation | |
| D Conflicting evidence Higher-quality studies conducted on this topic disagree with respect to their conclusions. The recommendation is based on these conflicting studies | |
| E Theoretical/ foundational evidence A preponderance of evidence from animal or cadaver studies, from conceptual models/principles, or from basic science/bench research supports this conclusion | |
| F Expert opinion Best practice based on the clinical experience of the guideline’s development team |