The current analysis compares changes in pain with changes in function and health status in individuals with painful diabetic peripheral neuropathy (DPN). The post hoc analysis is based on a 12week, multinational, placebo-controlled trial of pregabalin in which 401 patients were randomized to treatment. Study measures included the Brief Pain Inventory short-form (BPI-sf), EQ-5D and other patient-reported outcomes. Cutpoints were derived on the BPI-sf 0-10 average pain numeric rating scale [NRS] to classify pain grades of "mild" (1-3), moderate (4-6) and severe (7-10), adjusting for geographical regions where data were collected. Two different metrics were used to classify the importance of change in pain severity from baseline to 12weeks: changes in pain severity grades (defined by cutpoint categories) and percent reduction in the NRS (categories ranging from 0-9% to 50%). An improvement in one pain grade or a 30% reduction in the NRS served as determinants of a clinically important difference. Patients with a one-grade reduction in pain severity, either from "severe-to-moderate" or "moderate-to-mild," had a 3-point improvement the BPI-sf Pain Interference Index (PII; a composite measure of function); a reduction from "severe-to-mild" pain corresponded to a 6-point improvement in the PII. Similarly, a reduction in the NRS of 30% and 50% corresponded to a 3-point and a 5-point improvement in the PII, respectively. Changes in pain were also associated with changes in health status. Results suggest that patients whose pain is not reduced to a mild level of severity can still experience clinically important changes in function and health status.
