Survey of Cochrane protocols found methods for data extraction from figures not mentioned or unclear

Abstract

Objectives: To analyze whether protocols of Cochrane systematic reviews address data extraction from figures in included trials.

Study design and setting: Protocols of Cochrane systematic reviews published between May 2013 and May 2014 were screened by two authors independently, and the following data were collected: date of protocol publication, country of authors' origin, number of authors, number of affiliated institutions, Cochrane review group, whether the protocol contains description about data extraction from figures, method of data extraction from figures, and literature reference for a method of data extraction from figures.

Results: Among 589 protocols, 33 (5.6%) mentioned data extraction from figures in Methods section. Only one protocol specified that computer software will be used for data extraction from figures, one specifically indicated that data from figures will not be used, few stated estimation or approximation, whereas others did not provide any description of methodology for data extraction from figures.

Conclusion: Very few protocols of Cochrane systematic reviews mention data extraction from figures, and even when mentioned, methods for data extraction are unclear. Methodology for data extraction from figures should be incorporated into the Cochrane Handbook and new methodological standards for Cochrane systematic reviews.

Keywords: Computer software; Data extraction; Estimation; Figures; Graphical data; Methodology; Protocol; Systematic reviews; The Cochrane Library.