Influence of time, activities, and memory on the assessment of chronic low back pain intensity.

STUDY DESIGN: A prospective study. OBJECTIVE: To identify factors potentially influencing patient self-evaluation of chronic low back pain (CLBP) and their interactions. SUMMARY OF BACKGROUND DATA: The impact of the time, context, and/or recall on the self-assessment of chronic pain intensity remains poorly understood. METHODS: A prospective study investigated patients' CLBP intensity over 29 days. Patients were evaluated on days 1 and 29 by the investigator with a pain intensity visual analog scale (0-100), and interviewed by phone on days 8, 15, and 22 to 28 to evaluate pain intensity with a numerical rating scale (0-10), either thrice daily (time-associated group), or during rest/activities (activity-associated group). Current and/or recalled pain intensities were also assessed. Means of recorded pain intensity and overall assessment of patient's pain intensity of the day were subjected to statistical analyses with analysis of variance and test of correlation. RESULTS: Among the 203 patients included, 194 (56.2% women; mean age: 47.5 +/- 12.1 year) were considered in the analysis (9 patients were not followed until day 24). Strong correlations were obtained between mean pain intensity (time-associated group = 44 patients) and overall assessment of pain intensity of the day. Strong correlations were also obtained between overall assessment of pain intensity of the day and intensity measured during each activity, but not between current pain intensity and remembered pain 24 of 48 hours earlier (activity-associated group = 150 patients). Recalled pain intensities for the last 7 or 28 days were strongly correlated with current pain intensity, but the correlations were markedly weaker after adjustment for day 29-pain intensity. CONCLUSION: For CLBP patients, overall assessment of pain intensity of the day at evening is accurate to assess pain on 1 day. Overall assessment of pain intensity of the day is very close with usual pain. Furthermore, 24 and 48 hours remembered pain intensity are not accurate measures. Recalls of pain on the 7 or 28 last days were very dependant of the pain intensity of the day of the assessment. These findings could contribute to improving pain intensity assessment in CLBP patients avoiding multiple assessments, especially during clinical trials.