gms | German Medical Science

Background/research question: Systematic evidence syntheses depend on the quality of reporting and completeness of data in included studies. Cochrane guidance recommends that reviewers contact investigators to obtain missing information. The aim of this randomised study within a review (SWAR) was to compare the use of email main text or attachments as strategies for requesting information from study authors.

Methods: This SWAR [1] was embedded within a systematic review (SR) of studies with administrative/registry data investigating hospital volume-outcome relationships in total knee arthroplasty [2]. We randomised all 58 unique corresponding study authors included in the SR to receive personalised email requests for additional information as either email text (‘Email’ group) or attachment with self-developed, standardised data request forms (‘Attachment’ group). The primary outcome was the response rate, the secondary outcomes were the data completeness rate and the reviewer time invested in author contact. Response and data completeness rates were compared using the odds ratio (OR) and 95% confidence interval (CI). Reviewer time was compared using the mean difference and 95% CI.

Results: Of 58 study authors, N=29 were randomised to the Email group and N=29 to the Attachment group. One author in the Attachment group was later excluded from the study because the study was reclassified as ineligible for the SR. Basic characteristics of authors and studies were similar in both groups, but studies in the Email group tended to be more recently published. The response rate was 93% (n/N=27/29) in the Email and 75% (21/28) in the Attachment group (OR=4.5, 95% CI [0.9–24.0]). The completeness rate was 55% (16/29) in the Email and 36% (10/28) in the Attachment group (OR=2.2 [0.8–6.4]). The mean reviewer time (in minutes/author) was shorter in the Email (mean ± standard deviation 20.2±14.4) than in the Attachment group (31.8±14.4), mean difference 11.6 [4.1–19.1].

Conclusion: Personalised email requests elicited high response but only moderate data completeness rates regardless of the method, though both rates tended to be higher in the Email than in the Attachment group. Email requests as text took less reviewer time than creating attachments. Therefore, rather than attachments, we recommend personalised email texts for requesting additional data from study authors. The effectiveness of email text versus data collection forms needs to be validated for authors of studies with other designs, such as randomised controlled trials.

Competing interests: The authors declare that they have no conflict of interests.