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Wolff T, Witkop CT, Miller T, et al. Folic Acid Supplementation for the Prevention of Neural Tube Defects: An Update of the Evidence for the U.S. Preventive Services Task Force [Internet]. Rockville (MD): Agency for Healthcare Research and Quality (US); 2009 May. (Evidence Syntheses, No. 70.)

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Folic Acid Supplementation for the Prevention of Neural Tube Defects: An Update of the Evidence for the U.S. Preventive Services Task Force [Internet].

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Appendix 2. Uspstf Hierarchy of Research Design and Quality Rating Criteria 1, 2

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  • Poor: Outdated, irrelevant, or biased review without systematic search for studies, explicit selection criteria, or standard appraisal of studies.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

Appendix 2: Reference List

References

1.
Harris R, Atkins D, Berg AO, Best D, Eden KB, Feightner JW et al. US Preventive Services Task Force Procedure Manual. Rockville, MD: Agency for Healthcare Research and Quality, 2001.
2.
Harris RP, Helfand M, Woolf SH, Lohr KN, Mulrow CD, Teutsch SM. et al. Current methods of the US Preventive Services Task Force: a review of the process. Am J Prev Med. 2001;20(3 Suppl):21–35. [PubMed: 11306229]

Grant support

There was no grant support for this review.

Address for reprint requests

Reprints are available from the Agency for Healthcare Research and Quality Web site (www.ahrq.gov/clinic/uspstfix.htm).

Current addresses for all authors

  • Tracy Wolff, MD, MPH (Corresponding Author)
  • Medical Officer, USPSTF Program
  • Agency for Healthcare Research and Quality
  • 540 Gaither Road
  • Rockville, Maryland 20850
  • Therese Miller, DrPH
  • Senior Program Coordinator, USPSTF Program
  • Agency for Healthcare Research and Quality
  • 540 Gaither Road
  • Rockville, Maryland 20850
  • Shamsuzzoha B. Syed, MD, MPH, DPH (Cantab)

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