Table 2.

Criteria to assess the credibility of subgroup analyses. The greater the extent to which these criteria are met, the more plausible the putative subgroup effect.

Design

  • Is the subgroup variable a characteristic measured at baseline or after randomization?

  • Is the effect suggested by comparisons within rather than between studies?

  • Was the hypothesis specified a priori?

  • Was the direction of the subgroup effect specified a priori?

  • Was the subgroup effect one of a small number of hypothesized effects tested?


Analysis

  • Does the interaction test suggest a low likelihood that chance explains the apparent subgroup effect?

  • Is the significant subgroup effect independent?


Context

  • Is the size of the subgroup effect large?

  • Is the interaction consistent across studies?

  • Is the interaction consistent across closely related outcomes within the study?

  • Is there indirect evidence that supports the hypothesized interaction (biological rationale)?