Ensuring that only the most effective, best value health care interventions and service improvements are adopted and that there is disinvestment in ineffective procedures and practices is a major challenge facing health services around the world.

There is an ever-growing evidence base relating to the effectiveness and cost-effectiveness of health care interventions, but for clinicians and decision-makers this literature can be difficult and time consuming to identify and appraise. Funded by NIHR, the CRD databases are providing the solution.

The CRD databases are updated daily and provide decision-makers with access to:

• Over 20,000 quality assessed systematic reviews
• Over 13,000 economic evaluations
• Over 12,000 summaries of completed and ongoing health technology assessments
• Summaries of all Cochrane reviews and protocols

Although, the largest identifiable user of our databases is the NHS, we have a diverse audience with users all around the world.

In 2010, visitors from 199 countries viewed over four million records, free of charge, via the CRD website. This usage equates to an average viewing rate of one abstract every eight seconds.

Just over half of all records viewed were from DARE, around one quarter were from NHS EED and one fifth from HTA.

We also make our content accessible via a number other platforms.

We continue to provide full record content on a monthly basis to The Cochrane Library. We also supply on a monthly basis, brief records that include indexing and links to NHS Evidence so that our full content can be accessed directly from their site.

Other platforms that link directly through to our database records include the Trip Database, the Virtual Health Library, Health Systems Evidence, SUMSearch and the Knowledge Network of NHS Scotland.

DARE (Database of Abstracts of Reviews of Effects) is focused primarily on systematic reviews that evaluate the effects of health care interventions and the delivery and organisation of health services.

The database also includes reviews of the wider determinants of health such as housing, transport, and social care where these impact directly on health, or have the potential to impact on health.

Every week we undertake extensive searches and assess thousands of citations to identify potential systematic reviews. Full details of the search strategies are available on request (crd-info@york.ac.uk).

Those citations identified as potential systematic reviews are then independently assessed for inclusion by two researchers using the following criteria:

1. Were inclusion/exclusion criteria reported?
2. Was the search adequate?
3. Were the included studies synthesised?
4. Was the quality of the included studies assessed?
5. Are sufficient details about the individual included studies presented?

To be included, reviews must meet at least four criteria (criteria 1-3 are mandatory).

As soon as a review is identified as meeting the inclusion criteria, brief details are published on the database and the review is prioritised for abstract writing. Database users can request that we fast track the writing of individual critical abstracts (requests from the UK NHS get priority).

Critical abstracts are written and independently checked by researchers with in-depth knowledge and experience of systematic review methods. Each abstract contains a ‘bottom line’ summary of the topic, findings and reliability of the conclusions. Brief details are then given of the review methods, the results and conclusions and, uniquely, a critical assessment of the methods used and the reliability of the conclusions drawn. The purpose of this commentary is to help users of the database to judge the overall validity and reliability of the review.

Abstracts are checked and proof read by a technical editor to ensure consistency and readability prior to publishing. On final completion of an abstract, a copy is sent to the original authors for information. Authors are invited to reply with corrections to factual errors, and other relevant research. Where applicable, this information is added to the abstract.

DARE also includes records of all Cochrane reviews and protocols and provides details of those reviews that appear in publications other than in the Cochrane Library but are based on or related to a Cochrane review. Details of Campbell reviews are included where the interventions evaluated impact directly on health or have the potential to impact on health.

NHS EED (NHS Economic Evaluation Database) focuses primarily on the economic evaluation of health care interventions and aims to help decision makers interpret an increasingly complex and technical literature.

Economic evaluations are studies in which a comparison of two or more interventions or care alternatives is undertaken and in which both the costs and outcomes of the alternatives are examined. This includes cost-benefit analyses, cost-utility analyses, and cost-effectiveness analyses.

Each week extensive literature searches are undertaken to identify relevant economic evaluations. Full details of the search strategies are available on request (crd-info@york.ac.uk).

The citations are assessed by experienced health economists and classified by study design. As soon as a study is identified as meeting the inclusion criteria, brief details are published on the database and the study is prioritised for abstract writing.

Studies conducted in, or that are relevant to the UK health care system are considered priorities and fast tracked. This priority process ensures that evidence of most relevance to the NHS is made available in the form of a critical abstract as quickly as possible. As with DARE, database users can request that we fast track the writing of critical abstracts for individual studies (priority is given to the UK NHS).

Each abstract starts with a non technical summary of the topic, conclusions and reliability of the study.  A brief description of the effectiveness information on which the economic evidence is based and details of the key components of the economic evaluation, are also included. A critical commentary summarises the overall reliability and generalisability of the study, and presents any practical implications for the NHS.

Critical abstracts are written and independently checked by health economists with in-depth knowledge and experience of economic evaluation methods. They are then checked and proof read by a technical editor to ensure consistency and readability.

On final completion of an abstract, a copy is sent to the original authors for information. Authors are invited to reply with corrections to factual errors, further information and other research. Where applicable this information is added to the abstract.

The focus of the HTA database is on completed and ongoing health technology assessments from around the world. The HTA database is a valuable source for identifying grey literature as much of the information it contains is generally only available directly from individual funding agencies.

Database content is supplied by the 52 members of the International Network of Agencies for Health Technology Assessment (INAHTA) and 20 other HTA organisations around the world. Details of other on-going systematic reviews are also registered on the HTA database. All new content is checked, proof read and published on the database by the in house team at CRD.

The scope for inclusion is broad, encompassing any study designated as a health technology assessment by the contributing organisation.

Records for published projects contain full bibliographic details as well as contact information for the organisation publishing the report. Contributing organisations can also provide brief details of the authors’ conclusions if they wish. Links to reports, project pages and/ or organisation websites are provided wherever possible so database users can access full details directly.

The HTA database also contains brief details of ongoing HTA projects. These are updated when projects complete. This enables funders and researchers to identify work already in progress and may help reduce unintended duplication of effort.

Unlike the other CRD databases, DARE and NHS EED, the published records are not critically assessed. However, where a review or economic evaluation listed in the HTA database has met the inclusion criteria for DARE or NHS EED and a critical abstract has been written, links to that abstract are included in the HTA database record. Where available, links to INAHTA briefs and checklist are also provided.