Presentation 6: A preliminary investigation of patient-centered outcomes in patients with chronic pain1

Abstract Objective: To investigate patient-centered definitions of expected and successful treatment outcome for pain, fatigue, emotional distress, and interference with daily activities. Design: Cross-sectional study. Setting: Pain clinic. Participants: 110 patients (60 women) seeking treatment for chronic pain. Interventions: Not applicable. Main Outcome Measures: Patients were asked to complete the Patient Centered Outcomes Questionnaire (PCQ) before their treatment session. With the PCQ, patients used an 11-point numeric rating scale (NRS; range, 0 [none] to 10 [worst imaginable]) to rate 4 domains (pain, fatigue, emotional distress, interference with daily activities) over 4 different conditions (usual level past week, desired level after treatment, level associated with treatment success, expected level after treatment). The perceived importance of improvement in each domain was also assessed by the PCQ using an 11-point NRS (range, 0 [not at all important] to 10 [most important]). Descriptive statistics were generated for expected and successful treatment outcome for each domain. Then, repeated measures analyses of variance (ANOVAs) were used to determine if differences existed in the amount of change necessary for treatment success for each domain. Paired t tests were used to investigate the relationship between treatment success and expectation. Independent t tests were used to investigate sex differences in each of the domains and conditions. Exploratory cluster analysis was used to investigate the possibility of subgroups of patients based on their importance of improvement ratings. Results: Patients reported moderate levels of pain, fatigue, emotional distress, and life interference associated with their chronic pain conditions. Ratings of successful treatment for these domains ranged from 1.8 to 2.7. Patients considered mean reductions in pain of 3.44±1.85 points (56% reduction), in fatigue of 3.35±2.10 (57% reduction), in emotional distress of 3.64±2.90 (65% reduction), and in interference with daily activities 4.3±2.6 points (68% reduction) to be successful treatment outcomes. Results of the ANOVA omnibus test indicated a significant effect (F 3,324 =6.3, P P =.002) or fatigue reduction ( P =.002). When patients' expectations for treatment were compared with their criteria for success, only the interference domain differed ( t 103 =−2.5, P =.01). Patients expected that their posttreatment level of interference would be greater than they would consider successful treatment outcome. No sex comparisons for domains or conditions reached statistically reliable differences. Results of the hierarchical agglomerative cluster analysis (Ward's method, squared Euclidian distance) indicated a 3-cluster solution. Cluster 1 was comprised of persons with moderate importance ratings across all outcome domains. Cluster 2 was comprised of persons who had high ratings (nearly 10/10) for all domains. Cluster 3 was comprised of persons whose ratings suggested a greater relative interest in pain relief than the other outcome domains. Conclusions: Patient-centered definitions of treatment success appear to be larger than previous definitions that were based on statistical or clinical significance. In addition, patients believed larger improvements in interference with daily activities were warranted before treatment was considered successful (vs reduction in pain and fatigue). After treatment, patients expected to have higher levels of interference than what they would consider to be successful. These findings may partially explain continued health care utilization by patients with chronic pain. The finding of patient subgroups for importance of improvement in domains has implications for clinicians attempting to match treatment to patient goals. Future research projects that consider patient-centered and traditional definitions of treatment success would make valuable contributions to the literature.