4. Summarizing the evidence

Author(s): 
Jo.Robays
Author(s): 
Joan.Vlayen

Evidence must be summarized with results ideally coming from optimally conducted systematic reviews for each patient-important outcome. For each comparison of alternative management strategies, all outcomes should be presented together. It is likely that all studies relevant to a healthcare question will not provide evidence regarding every outcome. The GRADE working group has developed specific approaches to present the quality of the available evidence, the judgments that bear on the quality rating, and the effects of alternative management strategies on the outcomes of interest: the GRADE evidence profile (EP) and the Summary of Findings (SoF) table. An evidence profile is more detailed than a summary of findings table. The main difference is that it provides the detailed judgments and reasons for down- or upgrading per category (see below). As such, an evidence profile provides the information for other guideline developers and validators that allows them to understand how the judgment about the level of evidence was reached.

The GRADEpro software facilitates the process of developing both EPs and SoF tables.

The SoF table consists of 7 elements:

  1. A list of all important outcomes, both desirable and undesirable;
  2. A measure of the typical burden of these outcomes (e.g. control group, estimated risk);
  3. A measure of the risk in the intervention group or, alternatively or additionally, a measure of the difference between the risks with and without intervention;
  4. The relative magnitude of effect;
  5. Numbers of participants and studies addressing these outcomes;
  6. A rating of the overall confidence in effect estimates for each outcome (which may vary by outcome);
  7. Comments.

For binary outcomes, relative risks (RRs) are the preferred measure of relative effect and, in most instances, are applied to the baseline or control group risks to generate absolute risks. Ideally, the baseline risks come from observational studies including representative patients and identifying easily measured prognostic factors that define groups at differing risk. In the absence of such studies, relevant randomized trials provide estimates of baseline risk. When confidence intervals (CI) around the relative effect include no difference, one may simply state in the absolute risk column that results fail to show a difference, omit the point estimate and report only the CIs, or add a comment emphasizing the uncertainty associated with the point estimate.

On top of that GRADE provides a number of supplementary recommendations:

  • A SoF table should present the seven (or fewer) most important outcomes. These outcomes must always be patient-important outcomes and never be surrogates, although surrogates can be used to estimate effects on patient-important outcomes;
  • A SoF table should present the highest quality evidence;
  • When quality of two bodies of evidence (e.g. randomized trials and observational studies) is similar, a SoF table may include summaries from both.