Appendix B USPSTF Hierarchy of research design and quality rating criteria. 50

Publication Details

Hierarchy of Research Design

  • I Properly conducted randomized controlled trial (RCT)
  • II-1: Well-designed controlled trial without randomization
  • II-2: Well-designed cohort or case-control analytic study
  • II-3: Multiple time series with or without the intervention; dramatic results from uncontrolled experiments
  • III: Opinions of respected authorities, based on clinical experience; descriptive studies or case reports; reports of expert committees

Design-Specific Criteria

Systematic Reviews


  • Comprehensiveness of sources considered/search strategy used
  • Standard appraisal of included studies
  • Validity of conclusions
  • Recency and relevance are especially important for systematic reviews

Case-Control Studies


  • Accurate ascertainment of cases
  • Nonbiased selection of cases/controls with exclusion criteria applied equally to both
  • Response rate
  • Diagnostic testing procedures applied equally to each group
  • Measurement of exposure accurate and applied equally to each group
  • Appropriate attention to potential confounding variables

Randomized Controlled Trials and Cohort Studies


  • Initial assembly of comparable groups
    • -for RCTs: adequate randomization, including first concealment and whether potential confounders were distributed equally among groups.
    • -for cohort studies: consideration of potential confounders with either restriction or measurement for adjustment in the analysis; consideration of inception cohorts
  • Maintenance of comparable groups (includes attrition, crossovers, adherence, contamination)
  • Important differential loss to follow-up or overall high loss to follow-up
  • Measurements: equal, reliable, and valid (includes masking of outcome assessment)
  • Clear definition of the interventions
  • All important outcomes considered

Diagnostic Accuracy Studies


  • Screening test relevant, available for primary care, adequately described
  • Study uses a credible reference standard, performed regardless of test results
  • Reference standard interpreted independently of screening test
  • Handles indeterminate result in a reasonable manner
  • Spectrum of patients included in study
  • Sample size
  • Administration of reliable screening test