Re: The scatter of research: cross sectional comparison of randomised trials and systematic reviews across specialties
We read Hoffmann and colleagues paper  with interest, but are surprised that the authors make no mention of DARE (Database of Abstracts of Reviews of Effects), produced since 1994 by the Centre for Reviews and Dissemination and funded by the National Institute of Health Research. 
DARE focuses on systematic reviews that evaluate the effects of health and social care interventions and the delivery and organisation of care. The DARE process involves extensively searching for, identifying and critically appraising the global stock of systematic reviews.
The database is updated daily and currently provides access to over 11,000 quality-assessed and critically appraised systematic reviews as well as all Cochrane reviews and protocols. The database has become a key resource for health professionals and policy makers in almost 200 countries as not only is it the single place to search for systematic reviews but it provides users with a ‘bottom line’ on the overall validity and reliability of each review.
DARE content is also made available via The Cochrane Library. DARE and the Cochrane Database of Systematic Reviews together provide access to the most comprehensive collection of systematic reviews from around the world. CRD has recently entered into a new partnership with the National Library of Medicine in the USA to supply database content to PubMed Health. PubMed Health provides summaries and full text of selected systematic reviews to consumers and clinicians.
CRD also produces PROSPERO the first open access, online facility to prospectively register systematic reviews.[4,5] To date researchers from 33 countries have registered 535 systematic reviews. Once completed, reviews that meet the inclusion criteria will also be accessible via DARE. Together PROSPERO and DARE provide access to all ongoing and completed systematic reviews addressing questions about the effects of health and social care interventions.
 Hoffmann T, Erueti C, Thorning S, Glasziou P. The scatter of research: cross sectional comparison of randomised trials and systematic reviews across specialties. BMJ. 2012;344:e3223. doi: 10.1136/bmj.e3223.
 Centre for Reviews and Dissemination. DARE (Database of Abstracts of Reviews of Effects) http://www.crd.york.ac.uk/crdweb/
 Centre for Reviews and Dissemination. CRD announces new partnership with PubMed Health. (News Release) 9 December 2011.
 Booth A, Clarke M, Ghersi D, Moher D, Petticrew M, Stewart L. Establishing a Minimum Dataset for Prospective Registration of Systematic Reviews: An International Consultation. PLoS ONE 2011; 6(11): e27319.
 Booth A, Clarke M, Dooley G, Ghersi D, Moher D, Petticrew M, Stewart L. The nuts and bolts of PROSPERO: an international prospective register of systematic reviews. Systematic Reviews 2012; 1:2
Competing interests: We all contribute to the production and development of the CRD databases including DARE and PROSPERO.