On the importance of baseline pain intensity and measurement methods

Underestimating or Overestimating Improvement in Pain on a Smartphone Pain App: Role of Disability, Negative Affect, and Pain App Engagement

Clinicians often ask people with chronic pain about their perceived benefit from interventions designed to improve their pain. The aim of this study is to identify factors that contribute to underestimating or overestimating perceived changes in daily pain intensity over a month of daily assessments. We examined data from individuals with chronic pain who provided at least 28 daily assessments using a pain app as secondary analyses. Participants provided baseline demographic information and completed questionnaires assessing pain, activity interference, mood, pain disability, and catastrophizing. Using the pain app, they entered daily ratings of pain (0 = none, 10 = worst pain possible) and impressions of perceived day-to-day change (0 = better, 5 = same, and 10 = worse). Two hundred fifty-two (N = 252) subjects with chronic pain met the inclusion criteria of completing at least 28 daily assessments. Those who underestimated their improvement tended to have higher pain intensity at baseline (P < .001), reported greater activity interference and disability (P < .001), and were prone to greater catastrophizing and anxiety and depression (P < .01). People who were more accurate in assessing their improvement engaged less with the app with fewer 2-way messages compared with those who either underestimated or overestimated their improvement and who had more 2-way messaging (P < .05). This longitudinal study suggests that those who report greater levels of catastrophizing and anxiety and depression are more likely to underestimate any improvements in their pain over time but seem to engage more with a pain app. Future research will help in our understanding of what magnitude of perceived change in pain ratings is clinically meaningful. PERSPECTIVE: Those who report greater levels of pain, disability, anxiety, depression, and catastrophizing are most prone to underestimate improvements of their pain over time.

Optimizing Pain Intensity Assessment in Clinical Trials: How Many Ratings are Needed to Best Balance the Need for Validity and to Minimize Assessment Burden?

Pain intensity is the most commonly used outcome domain in pain clinical trials. To minimize the chances of type II error (ie, concluding that a treatment does not have beneficial effects, when in fact it does), the measure of pain intensity used should be sensitive to changes produced by effective pain treatments. Here we sought to identify the combination of pain intensity ratings that would balance the need for reliability and validity against the need to minimize assessment burden. We conducted secondary analyses using data from a completed 4-arm clinical trial of psychological pain treatments (N = 164 adults). Current, worst, least, and average pain intensity in the past 24 hours were assessed 4 times before and after treatment using 0 to 10 numerical rating scale-11. We created a variety of composite scores using these ratings and evaluated their reliability (Cronbach's alphas) and validity (ie, associations with a gold standard score created by averaging 16 ratings and sensitivity for detecting between-group differences in treatment efficacy). We found that for each measure, reliability increased as the number of ratings used to create the measures increased and that ratings from 3 or more days were needed to have adequately strong associations with the gold standard. Regarding sensitivity, the findings suggest that composite scores made up of ratings from 4 days are needed to maximize the chances of detecting treatment effects, especially with smaller sample sizes. In conclusion, using data from 3 or 4 days of assessment may be the best practice. PERSPECTIVE: Composite scores made up of at least 3 days of pain ratings appear to be needed to maximize reliability and validity while minimizing the assessment burden. TRIAL REGISTRATION: clinicaltrials.gov NCT01800604.