Appendix Table 2. U.S. Preventive Services Task Force Design-Specific Quality Rating Criteria

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.

RCTs 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.

Case—control studies
Criteria
   Accurate ascertainment of cases.
   Nonbiased selection of case-patients/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.

Diagnostic accuracy studies
Criteria
   Screening test relevant, available for primary care, adequately described.
   Credible reference standard used, performed regardless of test results.
   Reference standard interpreted independently of screening test.
   Indeterminate result handled in a reasonable manner.
   Adequate spectrum of patients included in study.
   Adequate sample size.
   Administration of reliable screening test.

RCT = randomized, controlled trial.

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