NICE process and methods

8 Selecting relevant evidence and data

8.1 Identifying appropriate studies and data

Searches should have been developed using the conceptual models to help identify the most appropriate types of evidence and data to include in the guidance and to inform analyses. Selection of evidence and data should also be informed by planned subsequent synthesis, including any network meta‑analysis. Otherwise the methods in chapter 6 of 'The guidelines manual' should be followed.

8.2 Extrapolation

In line with the methods outlined in section 9.1 of 'The guidelines manual', if very little, or no, good‑quality evidence is identified, the Committee may wish to extrapolate from high‑quality evidence in a related area. A number of service models have been developed from evidence for different clinical conditions. For example, recommendations in the Cancer service guidance[2] series were informed from evidence for a number of different cancer types and generalised across a number of others. The use of extrapolation must be considered carefully by the Committee, with explicit consideration of the features of the condition or interventions that allow extrapolation. This also applies when extrapolating findings from evidence in different healthcare settings. The Committee should comment on similarities in case mix, staffing, facilities and processes.

[2] To see a list of NICE cancer service guidance, type 'CSG' into the filter box on the linked 'Guidance list' page.