If secondary literature is inadequate, conflicting, or questions remain, search the primary literature for additional evidence
Therapy - RCT | Cohort Study | Case Control Study | Case Series
Diagnosis - Prospective Study - blind comparison to a gold standard | Cross-Sectional Study
Etiology/Harm - RCT | Cohort Study | Case Control Study | Case Series
Prognosis - Cohort Study | Case Control Study | Case Series
Prevention - RCT | Cohort Study | Case Control Study | Case Series