A quitting study has three or more groups: map the actual comparisons

Draw a comparison map

Cochrane describes multi-arm studies and the care needed when they contribute to evidence synthesis. For a reader, the first task is simpler: identify the arms the report names and the comparisons it actually presents. Write the intervention labels as described, without shortening them into misleading product names.

Use arrows only for comparisons you found in the report. An empty space between two groups means that comparison has not been verified in your reading; it does not mean the groups are equal or that the investigators must have tested them directly.

Cochrane: Chapter 23: Including variants on randomized trials

Use a fictional three-group example

Imagine a project with a planning note, a scheduled peer conversation and a combination of the two. Its summary reports the combination against the note. That fictional result does not automatically tell you how the conversation alone compares with either other group.

The combination also contains more than one component. You cannot attribute its entire result to a single part merely because that part interests you. The example is a map of questions, not a real trial or a claim about the effectiveness of any support format.

Keep shared groups attached to their source

If several comparisons use one common group, label it as the same group wherever it appears. Do not add its participant count repeatedly and report a larger unique study population. If a review combines comparisons, find the review’s own methods rather than building your own pooled result from the figure.

This does not require calculating an adjustment or selecting a preferred statistical method. It requires noticing that a repeated label can refer to the same people. Leave unclear pooling or weighting questions for the full methods and qualified appraisal.

Write the narrow conclusion you verified

Your note can say: “The summary reports combination versus note for the stated outcome; conversation-only comparisons remain unverified.” This is more useful than “all three were tested, so the best option is settled.” Check the period and uncertainty of the comparison you did locate.

The map cannot establish a ranking or recommend a personal treatment. It helps prevent a multi-group design from becoming several unsupported headlines. If the missing comparison matters to your care question, discuss the actual report and available options with an appropriate qualified professional.