The objective at this stage of the review process, which is highlighted in Figure 8.1, is to extract, from the reports of the primary studies, the data needed to address the research questions. The strategy for data extraction, including the data extraction form (or forms) needs to be defined and justified. The use of data extraction forms can help to maintain consistency (across studies and between extractors), and, where these are held electronically, the extraction and data recording can be performed in one step. Although the forms will have been piloted during the planning phase, it is possible that they will have to be revised during the data extraction stage when a broader range of studies are processed. Some tools that provide support for data extraction and subsequent data management are indicated in Chapter 13.