Expanding options for developing outcome measures from momentary assessment data

Objective: We propose several different patient-reported outcomes (PROs) from momentary, real-time collection of symptom data. In addition to the mean of momentary reports of symptoms, other types of summaries can reflect different aspects of the symptom experience. Methods: With secondary analyses of two studies of patients with chronic pain assessed with real-time methods, we demonstrate principles for developing outcomes that summarize symptom experience during a 1-week period. These studies focused on pain intensity, which is used to demonstrate methods for creating summary momentary measures. Results: Analyses from the first study (Pain 2008;139:146-57) yielded outcome measures based on the mean, median, 90th percentile, maximum, standard deviation, proportion of reports with no pain, proportion of reports with pain more than 50 (on a 0- to 100-point scale), and time-contingent measures. The second study examined the performance of these measures (and the mean) in a longitudinal study, in which some patients changed treatment (n = 78), making pain reduction likely, whereas others had no treatment change (n = 27). The measure that best discriminated the groups was the proportion of momentary reports without pain (effect size = 0.50), closely followed by the mean of all reports (effect size = 0.45). Most measures also correlated with patients' global impression of their change (between 0.39 and 0.55, except for standard deviation [0.13]). Conclusions: These analyses suggest that momentary symptom data can be useful for developing new PROs that reflect symptom experience other than the mean. They highlight knowledge gleaned from real-time studies, which deepens our understanding of symptoms by demonstrating which changes in symptoms are associated with overall perceived change.