Criteria for a judgment of “Yes” (i.e., low risk of bias)Any one of the following:
  • - No missing outcome data;
  • - Reasons for missing outcome data unlikely to be related to true outcome (for survival data, censoring unlikely to be introducing bias);
  • - Missing outcome data balanced in numbers across intervention groups, with similar reasons for missing data across groups;
  • - For dichotomous outcome data, the proportion of missing outcomes compared with observed event risk not enough to have a clinically relevant impact on the intervention effect estimate; *(see example below)
  • - For continuous outcome data, plausible effect size (difference in means or standardized difference in means) among missing outcomes not enough to have a clinically relevant impact on observed effect size;
  • - Missing data have been imputed using appropriate methods.
Criteria for the judgment of “No” (i.e., high risk of bias)Any one of the following:
  • - Reason for missing outcome data likely to be related to true outcome, with either imbalance in numbers or reasons for missing data across intervention groups;
  • - For dichotomous outcome data, the proportion of missing outcomes compared with observed event risk enough to induce clinically relevant bias in intervention effect estimate; ; *(see example below)
  • - For continuous outcome data, plausible effect size (difference in means or standardized difference in means) among missing outcomes enough to induce clinically relevant bias in observed effect size;
  • - “As-treated” analysis done with substantial departure of the intervention received from that assigned at randomization;
  • - Potentially inappropriate application of simple imputation.
Criteria for the judgment of “Can’t tell” (uncertain risk of bias)Any one of the following:
  • - Insufficient reporting of attrition/exclusions to permit judgment of “Yes” or “No” (e.g., number randomized not stated, no reasons for missing data provided);
  • - Study did not address/report this outcome.

From: Appendix D, Quality Assessment – RCTs

Cover of Preventing Alzheimer's Disease and Cognitive Decline
Preventing Alzheimer's Disease and Cognitive Decline.
Evidence Reports/Technology Assessments, No. 193.
Williams JW, Plassman BL, Burke J, et al.

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