Methodological issues affecting the value of patient-reported outcomes data.

The validity and value of patient-reported outcomes data are heavily dependent on the methods used to collect the data. This review examines the impact of a variety of methodological issues on the value of patient-reported outcome data. In particular, when patients are asked to self-monitor their experiences, disease episodes and healthcare utilization over time, a variety of methodological issues must be addressed if the data are to be considered a reliable and valid reflection of their daily lives. Ecological momentary assessment, a set of methods for collecting real-time data from patients in their natural environments, holds considerable promise as a way to enhance the value of certain types of patient-reported outcome data.