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Wolff T, Miller T, Ko S. Aspirin for the Primary Prevention of Cardiovascular Events: An Update of the Evidence for the U.S. Preventive Services Task Force [Internet]. Rockville (MD): Agency for Healthcare Research and Quality (US); 2009 Mar. (Evidence Syntheses, No. 68.)

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Aspirin for the Primary Prevention of Cardiovascular Events: An Update of the Evidence for the U.S. Preventive Services Task Force [Internet].

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Appendix USPSTF Hierarchy of Research Design and Quality Rating Criteria 6,7

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 and Quality Category Definitions

Systematic Reviews

Criteria

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

Definition of ratings from above criteria

Good: Recent, relevant review with comprehensive sources and search strategies; explicit and relevant selection criteria; standard appraisal of included studies; and valid conclusions.

Fair: Recent, relevant review that is not clearly biased but lacks comprehensive sources and search strategies.

Poor: Outdated, irrelevant, or biased review without systematic search for studies, explicit selection criteria, or standard appraisal of studies.

Case-Control Studies

Criteria

  • 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
  • Measurement of exposure accurate and applied equally to each group
  • Appropriate attention to potential confounding variables

Definition of ratings based on criteria above

Good: Appropriate ascertainment of cases and nonbiased selection of case and control participants; exclusion criteria applied equally to cases and controls; response rate equally to or greater than 80 percent; diagnostic procedures and measurements accurate and applied equally to cases and controls; and appropriate attention to confounding variables.

Fair: Recent, relevant, without major apparent selection or diagnostic work-up bias but with response rates less than 80 percent or attention to some but not all important confounding variables.

Poor: Major section or diagnostic work-up biases, response rates less than 50 percent, or inattention to confounding variables.

Randomized Controlled Trials and Cohort Studies

Criteria

  • 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

Definition of ratings based on above criteria

Good: Evaluates relevant available screening tests; uses a credible reference standard; interprets reference standard independently of screening test; reliability of test assessed; has few or handles indeterminate results in a reasonable manner; includes large number (more than 100 broad-spectrum of patients.

Fair: Evaluates relevant available screening tests; uses reasonable although not best standard; interprets reference standard independent of screening test; moderate sample size (50 to 100 subjects) and a “medium” spectrum of patients.

Poor: Has fatal flaw such as: Uses inappropriate reference standard; screening test improperly administered; biased ascertainment of reference standard; very small sample size or very narrow selected spectrum of patients.

Diagnostic Accuracy Studies

Criteria

  • 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

Definition of ratings based on above criteria

Good: Evaluates relevant available screening test; uses a credible reference standard; interprets reference standard independently of screening test; reliability of test assessed; has few or handles indeterminate results in a reasonable manner; includes large number (more than 100) broad-spectrum patients with and without disease.

Fair: Evaluates relevant available screening test; uses reasonable although not best standard; interprets reference standard independent of screening test; moderate sample size (50–100 subjects) and a “medium” spectrum of patients.

Poor: Has fatal flaw such as: Uses inappropriate reference standard; screening test improperly administered; biased ascertainment of reference standard; very small sample size or very narrow selected spectrum patients.

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