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Table 1 Algorithm for categorizing the “main” outcome domain for each systematic review

From: Outcome choice and definition in systematic reviews leads to few eligible studies included in meta-analyses: a case study

Scenario

If

Then

Number of systematic reviews (N = 175)

n (%)

1

The review named only 1 primary outcome domain

we categorized that outcome domain as the main outcome domain.

131 (75)

2

The review named >1 primary outcome domain

we categorized the primary outcome domain with the highest number of included studies as the main outcome domain.

41 (23)

3

The review did not name any primary outcome domain, but named ≥1 secondary outcome domain

we categorized the secondary outcome domain with the highest number of included studies as the main outcome domain.

0 (0)

4

If the review did not name any primary or secondary outcome domains

we categorized the “other” (i.e., non-primary and non-secondary) outcome domain with the highest number of included studies as the main outcome domain.

3 (2)

  1. Note
  2. In scenarios 2, 3, and 4, if there were two or more possible outcome domains that had the same number of included studies (“Then” column), we categorized the first outcome listed in the Methods section as the main outcome domain