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Table 1 Questions on contacting of authors for the cross-sectional study

From: Contacting of authors by systematic reviewers: protocol for a cross-sectional study and a survey

Section

Questions and answers and criteria for addressing questions

Reporting on contacting of studies

Question 1. Did the reviewers report that they contacted studies?

 Answer 1. Yes/no

Criteria for addressing question 1:

 Yes: When the reviewers report that they contacted one or more studies to obtain additional information. “Yes” is also scored when reviewers reported that they wanted to contact one or more of these studies, but contact information could not be obtained.

 No: When the reviewers did not report whether studies were contacted to obtain additional information.

 No: When reviewers report that they did not contact studies to obtain additional information.

 “No” is also scored when reviewers describe that they planned to contact studies in the methods section, but do not further report on contacting studies.

 “No” is also scored when in the section “Contribution of Authors” specific reviewers are linked to contacting authors without further specification, but in the review itself there is no reported proof that studies were actually contacted. The rationale for this “No” score is that such linking could indeed refer to contacting of studies to obtain additional information (e.g., missing data and risk of bias), but could also refer to contacting of authors to assess the eligibility of studies or contacting of authors to identify additional or ongoing studies.

Reporting on contacting of studies with “Unclear” risk of bias domainsa

Question 2. Did the reviewers report that all studies with at least one “Unclear” (as a result of missing or insufficient information) risk of bias score were contacted?

 Answer 2. Yes/no/not applicable (NA)

Criteria for addressing question 2:

 Yes: Studies were contacted and all studies with at least one “Unclear” (as a result of missing or insufficient information) risk of bias score were contacted. We will still score “Yes” when reviewers reported that they wanted to contact all studies with “Unclear” (as a result of missing or insufficient information) risk of bias scores, but contact information could not be obtained for one or more of these studies.

 No: Studies were contacted, but not all studies with at least one “Unclear” (as a result of missing or insufficient information) risk of bias score were contacted.

 NA: Studies were contacted, but “Unclear” (as a result of missing or insufficient information) risk of bias scores were not assigned to any of the domains of the included studies.

Reporting all contacted studies

Question 3. Could the number of all contacted studies be identified in the review?

 Answer 3. Yes/no

Criteria for addressing question 3:

 Yes: When the number of all contacted studies could be identified in the review. We still scored “Yes” when reviewers reported that they wanted to contact one or more of these studies, but contact information could not be obtained.

 No: When the number of all contacted studies could not be identified in the review.

 No: When one or more studies have been contacted, but it was impossible to identify the exact total number of studies that were contacted.

Number of contacted studies

Question 4. What is the number of contacted studies in the review?

 Answer 4. Present the number of contacted studies in the review.

Criteria for addressing question 4:

 Only the actual number of studies that was contacted will be scored. Studies that were not contacted because contact information was not available will not be included in this number.

Reporting all replying studies

Question 5. Could the number of all replying studies be identified in the review?

 Answer 5. Yes/no

Criteria for addressing question 5:

 Yes: When the number of all replying studies could be identified in the review.

 No: When the number of all replying studies could not be identified (e.g., as a result of unclear reporting) in the review.

 No: When one or more contacted studies replied, but it was impossible to identify the exact total number of studies that replied.

Number of replying studies

Question 6. What is the number of contacted studies in the review that replied?

 Answer 6. Present the number of studies that replied.

Criteria for addressing question 6:

 The actual number of studies that replied will be scored.

Reporting on obtained additional information data

Question 7. Did the reviewers report what information data was(were) obtained from each of the replying studies?

 Answer 7. Yes/no

Criteria for addressing question 7:

 Yes: The reviewers reported what information data was(were) obtained from each of the replying studies.

 Yes: The reviewers reported that the replying studies explained that they could not provide the requested data.

 No: The reviewers did not report what information data was(were) obtained from each of the replying studies.

 No: The reviewers reported that information data was(were) obtained from the replying studies, but this was partially reported or it was unclear what these data were.

Reporting on the consequences of obtained additional information data

Question 8. Were the consequences (e.g., modified statistics and risk of bias or GRADE scores) of each of the obtained information data reported?

 Answer 8. Yes/no

Criteria for addressing question 8:

 Yes: The review reported the consequences of each of the obtained information data.

 No: The review did not report the consequences of any of the obtained information data.

 No: The review reported the consequences of some obtained information data, but not for each of the obtained information data.

  1. aHiggins et al. [47] divide the definition of “Unclear” risk of bias in three subgroups: Studies are assessed as at unclear risk of bias (1) when too few details are available to make a judgement of “high” or “low” risk; (2) when the risk of bias is genuinely unknown despite sufficient information about the conduct; or (3) when an entry is not relevant to a study (for example because the study did not address any of the outcomes in the group of outcomes to which the entry applies). In this cross-sectional study, we only refer to contacting of authors for the first subgroup of the definition of “Unclear” risk of bias by Higgins et al. [47].