• James Marcus, Kathryn Lasch, Yin Wan, Mei Yang, Ching Hsu, and Domenico Merante.
• Pharmerit International, Bethesda, MD, USA.
• Pain Res Manag. 2018 Jan 1; 2018: 2140420.

ObjectivesUsing patient global impression of change (PGIC) as an anchor, an approximately 30% reduction on an 11-point numeric pain intensity rating scale (PI-NRS) is considered a clinically important difference (CID) in pain. Our objective was to define the CID for another pain measure, the worst pain severity (WPS) item of the modified Brief Pain Inventory (m-BPI).MethodsIn this post hoc analysis of a double-blind, placebo-controlled, phase 2 study, 452 randomized patients with diabetic peripheral neuropathic pain (DPNP) were followed over 5 weeks, with m-BPI data collected weekly and PGIC at treatment conclusion. Receiver operating characteristic (ROC) curves (via logistic regression) were used to determine the changes in the m-BPI-WPS score that best predicted ordinal clinical improvement thresholds (i.e., "minimally improved" or better) on the PGIC.ResultsSimilar to the PI-NRS, a change of -3 (raw) or -33.3% from the baseline on the m-BPI-WPS optimized prediction for the "much improved" or better PGIC threshold and represents a CID. There was a high correspondence between observed and predicted PGIC categories at each PGIC threshold (ROC AUCs were 0.78-0.82).ConclusionsWorst pain on the m-BPI may be used to assess clinically important improvements in DPNP studies. Findings require validation in larger studies.

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