Data based on HRGs may not be appropriate in all circumstances. For example, when the new technology and the comparator both fall under the same HRG, or when the mean cost does not reflect resource use in relation to the new technology under evaluation. In such cases, other sources of evidence, such as micro-costing studies, may be more appropriate. In all cases, include all relevant costs such as the costs of the test, follow up, treatment, monitoring, staffing, facilities, training and any other modifications needed. When cost data is taken from literature, the methods used to identify sources of costs and resource use should be defined (preferably through systematic review). When multiple or alternative sources are available, the choice for the base case should be justified, the discrepancies between the sources should be explained and sensitivity analyses explored when appropriate implications for results of using alternative data sources.