Background: There is increased pressure to conduct systematic reviews as comprehensively as possible within the constraints of a timescale that meets the needs of policy makers.

Objectives: We aimed to evaluate how the findings and conclusions of a full Cochrane systematic review differ when certain aspects of the methodology are limited in order to conduct a more rapid systematic synthesis of the evidence.

Methods: Blinded to the results of a Cochrane systematic review on the effectiveness of directly observed therapy for treating tuberculosis, we limited three key features of the Cochrane review protocol. 1) The literature search: using the same key words as those used in the full Cochrane review, we reduced the number of databases searched; 2) study selection: using the same inclusion criteria as the Cochrane review, we used only one researcher to select studies; and 3) data collection and synthesis: using the same data collection and synthesis procedures to meta-analyse the data, we used only one researcher to extract the data. Any queries regarding study selection and data collection were resolved with a second researcher.

Results: The results compare how limiting certain aspects of the methodology of a full systematic review impact on: 1) the studies identified from the search; 2) the studies included into the review after screening; and 3) the results of the meta-analysis after data collection.

Conclusions: The results of this more rapid systematic synthesis of data are compared with those of the Cochrane review to understand how limiting methodological aspects impact on the conclusions which can be drawn for policy makers. Based on these findings, the benefits and limitations of each approach are discussed, as are the limitations of the study.