Open Access Open Badges Methodology

A surveillance system to assess the need for updating systematic reviews

Nadera Ahmadzai1*, Sydne J Newberry2, Margaret A Maglione2, Alexander Tsertsvadze1, Mohammed T Ansari1, Susanne Hempel2, Aneesa Motala2, Sophia Tsouros1, Jennifer J Schneider Chafen3, Roberta Shanman2, David Moher1 and Paul G Shekelle24

Author Affiliations

1 Knowledge Synthesis Group, Ottawa Hospital Research Institute, Clinical Epidemiology Program, Center for Practice-Changing Research, 501 Smyth Road, Ottawa, ON K1H 8L6, Canada

2 Southern California Evidence-based Practice Center (SCEPC), The RAND Corporation, 1776 Main Street, PO Box 2138, Santa Monica, CA 90401, USA

3 Stanford University, Stanford University 117 Encina Commons, Stanford, CA 94305-6019, USA

4 Veterans Affairs Greater Los Angeles Healthcare System, 11301 Wilshire Boulevard, Los Angeles, CA 90073, USA

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Systematic Reviews 2013, 2:104  doi:10.1186/2046-4053-2-104

Published: 14 November 2013



Systematic reviews (SRs) can become outdated as new evidence emerges over time. Organizations that produce SRs need a surveillance method to determine when reviews are likely to require updating. This report describes the development and initial results of a surveillance system to assess SRs produced by the Agency for Healthcare Research and Quality (AHRQ) Evidence-based Practice Center (EPC) Program.


Twenty-four SRs were assessed using existing methods that incorporate limited literature searches, expert opinion, and quantitative methods for the presence of signals triggering the need for updating. The system was designed to begin surveillance six months after the release of the original review, and thenceforth every six months for any review not classified as being a high priority for updating. The outcome of each round of surveillance was a classification of the SR as being low, medium or high priority for updating.


Twenty-four SRs underwent surveillance at least once, and ten underwent surveillance a second time during the 18 months of the program. Two SRs were classified as high, five as medium, and 17 as low priority for updating. The time lapse between the searches conducted for the original reports and the updated searches (search time lapse - STL) ranged from 11 months to 62 months: The STL for the high priority reports were 29 months and 54 months; those for medium priority reports ranged from 19 to 62 months; and those for low priority reports ranged from 11 to 33 months. Neither the STL nor the number of new relevant articles was perfectly associated with a signal for updating. Challenges of implementing the surveillance system included determining what constituted the actual conclusions of an SR that required assessing; and sometimes poor response rates of experts.


In this system of regular surveillance of 24 systematic reviews on a variety of clinical interventions produced by a leading organization, about 70% of reviews were determined to have a low priority for updating. Evidence suggests that the time period for surveillance is yearly rather than the six months used in this project.

Systematic review; Updating; Surveillance