Expanding options for developing outcome measures from momentary assessment data

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.

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.

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]).

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.