Reviews may need to be updated for a number of reasons:

• if new studies are found that could change the conclusions of the review,
• if there is ongoing uncertainty and new evidence could change practice,
• if an update has been commissioned by a guideline maker, 
• if new methods need to be incorporated.

Once an update has been agreed between authors and the review group, the process for the CIS is similar to the initial review. The search strategies will need to be checked and updated if necessary. The range of resources to be searched should also be evaluated; some sources may not be included in the update if access is no longer available or if they were not considered valuable in the initial searches. Equally, additional resources might be suggested by the CIS if they feel it is appropriate. The CIS will then arrange a suitable timescale with the authors for running the searches, and then provide the de-duplicated results to them.

The same 12 month deadline for the searches to be considered current, applies to updates, therefore top up searches may be needed.

The authors will then submit a draft update review and after all editorial comments have been addressed by the authors, the update will be published.