Author queries via email text elicited high response and took less reviewer time than data forms - a randomised study within a review.

Objective: To compare two strategies for requesting additional information for systematic reviews (SR) from study authors.

Study Design And Setting: Randomised study within a SR of hospital volume-outcome relationships in total knee arthroplasty. We sent personalized email requests for additional information to study authors as either email text ("Email" group) or attachment with self-developed, personalised 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.

Results: Of 57 study authors, 29 were randomised to the Email group and 28 to the Attachment group. The response rate was 93% for Email and 75% for Attachment (odds ratio 4.5, 95% confidence interval [0.9-24.0]). Complete data were provided by 55% (Email) vs. 36% (Attachment) of authors (odds ratio 2.2 [0.8-6.4]). The mean reviewer time was shorter in the Email (mean ± standard deviation of 20.2±14.4 minutes/author) than the Attachment group (31.8±14.4 minutes/author) with a mean difference of 11.6 [4.1-19.1] minutes/author.

Conclusion: Personalised email requests elicited high response but only moderate data completeness rates regardless of the method (email text or attachment). Email requests as text took less reviewer time than creating attachments.