Table 2

Summary of reasons for duplications from respondents of the questionnaire

Response to screening questionResponses in survey
Not similar

  • Different objectives or planned analyses.

  • Poor quality of previous systematic reviews.

  • Duplication was needed owing to the rapid rate that new studies on COVID-19 were being published.

Sufficiently different

  • Differences in PICOS, study design or planned analyses.

  • Differences in databases searched.

  • Poor quality of previous systematic reviews.

  • Duplication was needed owing to the rapid rate that new studies on COVID-19 were being published.

Repetition needed

  • No systematic review was published or completed at the time of registration.

  • Repetition was needed to confirm/refute previous systematic review conclusions.*

  • *Neither respondent provided reasons in their registration record.

  • PICOS, Population, Intervention/Exposure, Comparator, Outcome, Study Design.