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Nygren P, Fu R, Freeman M, et al. Screening and Treatment for Bacterial Vaginosis in Pregnancy: Systematic Review to Update the 2001 U.S. Preventive Services Task Force Recommendation [Internet]. Rockville (MD): Agency for Healthcare Research and Quality (US); 2008 Jan. (Evidence Syntheses, No. 57.)

Appendix D. Study Quality Criteria

US Preventive Services Task Force Quality Rating Criteria*

Randomized Controlled Trials (RCTs) and Cohort Studies

Criteria

  • Initial assembly of comparable groups: RCTs—adequate randomization, including concealment and whether potential confounders were distributed equally among groups; 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 interventions
  • Important outcomes considered
  • Analysis: adjustment for potential confounders for cohort studies, or intension-to-treat analysis for RCTs

Definition of ratings based on above criteria

Good: Meets all criteria: Comparable groups are assembled initially and maintained throughout the study (follow-up at least 80 percent); reliable and valid measurement instruments are used and applied equally to the groups; interventions are spelled out clearly; important outcomes are considered; and appropriate attention to confounders in analysis.

Fair: Studies will be graded “fair” if any or all of the following problems occur, without the important limitations noted in the “poor” category below: Generally comparable groups are assembled initially but some question remains whether some (although not major) differences occurred in follow-up; measurement instruments are acceptable (although not the best) and generally applied equally; some but not all important outcomes are considered; and some but not all potential confounders are accounted for.

Poor: Studies will be graded “poor” if any of the following major limitations exists: Groups assembled initially are not close to being comparable or maintained throughout the study; unreliable or invalid measurement instruments are used or not applied at all equally among groups (including not masking outcome assessment); and key confounders are given little or no attention.

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 results 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 to 100 subjects) and a “medium” spectrum of patients.
  • Poor: Has important limitation such as: uses inappropriate reference standard; screening test improperly administered; biased ascertainment of reference standard; very small sample size of very narrow selected spectrum of patients.

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
  • Appropriate attention to potential confounding variable

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 equal 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 rate less than 80 percent or attention to some but not all important confounding variables.
  • Poor: Major selection or diagnostic work-up biases, response rates less than 50 percent, or inattention to confounding variables.

Jadad Scale Criteria

A numerical score between 0–5 is assigned as a rough measure of study design/reporting quality (0 being weakest and 5 being strongest). This number is based on the validated scale developed by Jadad et al.

This calculation does not account for all study elements that may be used to assess quality (other aspects of study design/reporting are addressed in tables and text).

A Jadad score is calculated using the seven items in the table below. The first five items are indications of good quality, and each counts as one point towards an overall quality score. [Either give a score of 1 point for each “yes” or 0 points for each “no.” There are no in-between marks.]

The final two items indicate poor quality, and a point is subtracted for each if its criteria are met. The range of possible scores is 0 to 5.

Jadad Score Calculation
ItemScore
Was the study described as randomized (this includes words such as randomly, random, and randomization)?0/1
Was the method used to generate the sequence of randomization described and appropriate (table of random numbers, computer-generated, etc)?0/1
Was the study described as double blind?0/1
Was the method of double blinding described and appropriate (identical placebo, active placebo, dummy, etc)?0/1
Was there a description of withdrawals and dropouts?0/1
Deduct one point if the method used to generate the sequence of randomization was described and it was inappropriate (patients were allocated alternately, or according to date of birth, hospital number, etc).0/-1
Deduct one point if the study was described as double blind but the method of blinding was inappropriate (e.g., comparison of tablet vs. injection with no double dummy).0/-1

Randomization. A method to generate the sequence of randomization will be regarded as appropriate if it allowed each study participant to have the same chance of receiving each intervention and the investigators could not predict which treatment was next. Methods of allocation using date of birth, date of admission, hospital numbers, or alternation should be not regarded as appropriate.

Double blinding. A study must be regarded as double blind if the word “double blind” is used. The method will be regarded as appropriate if it is stated that neither the person doing the assessments nor the study participant could identify the intervention being assessed, or if in the absence of such a statement the use of active placebos, identical placebos, or dummies is mentioned.

Withdrawals and dropouts. Participants who were included in the study but did not complete the observation period or who were not included in the analysis must be described. The number and the reasons for withdrawal in each group must be stated. If there were no withdrawals, it should be stated in the article. If there is no statement on withdrawals, this item must be given no points.

Created using information from Harris et al. Current Methods of the USPSTF: A Review of the Process. Am J Prev Med. 2001:20(3S);21–35.

Jadad AR, Moore RA, Carroll D, et al. Assessing the quality of reports of randomized clinical trials: is blinding necessary? Controlled Clinical Trials 1996;17[1]:1–12

Footnotes

*

Created using information from Harris et al. Current Methods of the USPSTF: A Review of the Process. Am J Prev Med. 2001:20(3S);21–35.

Jadad AR, Moore RA, Carroll D, et al. Assessing the quality of reports of randomized clinical trials: is blinding necessary? Controlled Clinical Trials 1996;17[1]:1–12

Cover of Screening and Treatment for Bacterial Vaginosis in Pregnancy: Systematic Review to Update the 2001 U.S. Preventive Services Task Force Recommendation
Screening and Treatment for Bacterial Vaginosis in Pregnancy: Systematic Review to Update the 2001 U.S. Preventive Services Task Force Recommendation [Internet].
Evidence Syntheses, No. 57.
Nygren P, Fu R, Freeman M, et al.

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