Therapy /Prevention, Aetiology/Harm | Prognosis | Diagnosis | Differential diagnosis/ symptom prevalence | Economic and decision analysis | |
---|---|---|---|---|---|
Investigating the effect of patient characteristic on the outcome of disease | Investigating a diagnostic test. Is this diagnostic test accurate? | ||||
Level 1 | Systematic Review of randomized trials(RT) | Systematic Review of inception cohort studies | Systematic Review of level 1 diagnostic studies | Systematic Review of prospective or classic cohort | Systematic Review of level 1 economic studies |
High quality RT(e.g.:> 80% follow up, narrow confident interval) | Individual cohort study with > 80% follow up, all patient enrolled at the same time | Level 1 diagnostic studies or Validating studies which test the quality of a specific diagnostic test, previously developed, in series of consecutive patients with reference “gold” standard | Prospective or classic cohort studies with good follow up (>80%) | Level 1 studies (analysis based on clinically sensible costs or alternative, values obtained from many studies, and including multiway sensitive analysis | |
Level 2 | Systematic Review of cohort studies | Systematic Review of either historical cohort study or untreated control groups (control arm) in RCTs | Systematic Review of level 2 diagnostic studies | Systematic Review of level 2 studies | Systematic Review of level 2 studies |
Lesser quality RT (e.g.: <80% follow up, wide confident interval, no clear randomization, problems with blinding, etc.) | Historical (retrospective) cohort study or control arm from a RCT | Level 2 diagnostic studies or Exploratory studies which collect information, trawl data to find which factor are significant (e.g.: using regression analysis) | Level 2 studies (retrospective or historical cohort study or with follow up <80%) | Level 2 studies (analysis based on clinically sensible cost or alternative from limited studies, and including multiway sensitivity analysis. | |
Individual Cohort study, including matched cohort studies (prospective comparative studies) | Ecological Studies | ||||
Ecological Studies | |||||
Level 3 | Systematic Review of case–control studies | Systematic Review of level 3 studies | Systematic Review of level 3 studies | Systematic Review of level 3 studies | |
Individual case–control study | Level 3 diagnostic studies or studies in non-consecutive patients and without consistently reference “gold” standards | Level 3 studies (non-consecutive cohort or very limited population) | Level 3 studies (analysis based on poor alternative or costs, poor quality estimates of data, but including sensitivity analysis | ||
Level 4 | Case-series | Case-series | Case–control study | Case-series | No sensitivity analysis |
Poor quality cohort and case–control studies* | Poor quality cohort and case–control studies* | Poor or non independent reference standard | |||
Level 5 | Expert opinion | Expert opinion | Expert opinion | Expert opinion | Expert opinion |