Measurement strategies for indirect costs in economic evaluations

Considerable research has been undertaken on the different methods for valuing work absences and productivity losses (e.g., human capital vs. friction costing). However, investigation related to the best way to capture this information directly from trial participants or through surveys has been inadequate. The collection of information that may be used in providing estimates of indirect costs is problematic for a number of reasons such as the presence of poor questionnaire design, a lack of psychometric testing and accessible validating data and the potential for recall errors. In this review, the measurement methods of lost time for work activities are examined. Issues in the validity of existing instruments and recall periods are explored. Based on a review of the literature, the relevance of generic and specific methods of measuring work losses are assessed.