From: The impact of orthodontic treatment on the quality of life a systematic review
Level | Therapy/Prevention,aetiology/Harm | Prognosis | Diagnosis | Differential diagnosis/symptom prevalence study | Economic and decision analyses |
---|---|---|---|---|---|
1a | SR (with homogeneity) of RCTs | SR (with homogeneity) of inception cohort studies; validated in different populations | SR (with homogeneity) of Level 1 diagnostic studies; with 1b studies from different clinical centres | SR (with homogeneity) of prospective cohort studies | SR (with homogeneity) of Level 1 economic studies |
1b | Individual RCT (with narrow Confidence Interval) | Individual inception cohort study with > 80% follow-up; validated in a single population | Validating cohort study with good reference standards; or tested within one clinical centre | Prospective cohort study with good follow-up | Analysis based on clinically sensible costs or alternatives; systematic review(s) of the evidence; and including multi-way sensitivity analyses |
1c | All or none | All or none case-series | All or none case-series | Absolute better-value or worse-value analyses | |
2a | SR (with homogeneity) of cohort studies | SR (with homogeneity) of either retrospective cohort studies or untreated control groups in RCTs | SR (with homogeneity) of Level >2 diagnostic studies | SR (with homogeneity) of 2b and better studies | SR (with homogeneity) of Level >2 economic studies |
2b | Individual cohort study (including low quality RCT; e.g., <80% follow-up) | Retrospective cohort study or follow-up of untreated control patients in an RCT; Derivation of CDR or validated on split-samples only | Exploratory cohort study with good reference standards; after derivation, or validated only on split-samples or databases | Retrospective cohort study, or poor follow-up | Analysis based on clinically sensible costs or alternatives; limited review(s) of the evidence, or single studies; and including multi-way sensitivity analyses |
2c | “Outcomes” Research; Ecological studies | “Outcomes” Research | Ecological studies | Audit or outcomes research | |
3a | SR (with homogeneity) of case-control studies | SR (with homogeneity) of 3b and better studies | SR (with homogeneity) of 3b and better studies | SR (with homogeneity) of 3b and better studies | |
3b | Individual Case-Control Study | Non-consecutive study; or without consistently applied reference standards | Non-consecutive cohort study, or very limited population | Analysis based on limited alternatives or costs, poor quality estimates of data, but including sensitivity analyses incorporating clinically sensible variations. | |
4 | Case-series (and poor quality cohort and case-control studies) | Case-series (and poor quality prognostic cohort studies) | Case-control study, poor or non-independent reference standard | Case-series or superseded reference standards | Analysis with no sensitivity analysis |
5 | Expert opinion without explicit critical appraisal, or based on physiology, bench research or “first principles” | Expert opinion without explicit critical appraisal, or based on physiology, bench research or “first principles” | Expert opinion without explicit critical appraisal, or based on physiology, bench research or “first principles” | Expert opinion without explicit critical appraisal, or based on physiology, bench research or “first principles” | Expert opinion without explicit critical appraisal, or based on economic theory or “first principles” |