Ambulatory and diary methods can facilitate the measurement of patient-reported outcomes

Stefan Schneider, Arthur A. Stone

Ambulatory and diary methods of self-reported symptoms and well-being have received increasing interest in recent years. These methods are a valuable addition to traditional strategies for the assessment of patient-reported outcomes (PROs) in that they capture patients' recent symptom experiences repeatedly in their natural environments. In this article, we review ways that incorporating diary methods into PRO measurement can facilitate research on quality of life. Several diary methods are currently available, and they include "real-time" (Ecological Momentary Assessment) and "near-real-time" (end-of-day assessments, Day Reconstruction Method) formats. We identify the key benefits of these methods for PRO research. (1) In validity testing, diary assessments can serve as a standard for evaluating the ecological validity and for identifying recall biases of PRO instruments with longer-term recall formats. (2) In research and clinical settings, diaries have the ability to closely capture variations and dynamic changes in quality of life that are difficult or not possible to obtain from traditional PRO assessments. (3) In test construction, repeated diary assessments can expand understanding of the measurement characteristics (e.g., reliability, dimensionality) of PROs in that parameters for differences between people can be compared with those for variation within people. Diary assessment strategies can enrich the repertoire of PRO assessment tools and enhance the measurement of patients' quality of life.