INTRODUCTION: Pain is a common and often debilitating sequela of burn injury. Burn pain develops following damage to peripheral sensory nerves and the release of inflammatory mediators from injury. Burn pain is complex and can include background and procedural pain that result from the injury itself, wound care, stretching, and surgery. Clinicians and researchers need valid and reliable pain measures to guide screening, treatment, and research protocols. Unlike other conditions, visual analog, or numeric pain rating scale (VAS/NRS) scores that represent mild, moderate, and severe pain among people with burn injury have not been established. The aim of this study was to identify the most suitable average pain intensity rating scores for mild, moderate, and severe pain in adult burn survivors using a PROMIS Pain Interference (PROMIS-PI) short form.

METHODS: An average pain intensity VAS/NRS score (0-10) and customized PROMIS-PI short form were administered to adults with burn injury treated at a regional burn center at hospital discharge (baseline) and at 6, 12, and 24-months after injury. To identify pain intensity scores that represent mild, moderate, and severe pain, we computed F values and Bayesian Information Criterion (BIC) statistics associated with multiple ANOVA comparisons for mean pain interference scores by various pain intensity cut points. Six possible cut points (CP) were compared: CP 3,6; 3,7; 4,6; 4,7; 2,5; and 3,5. Optimal cut points were considered those with the highest ANOVA F statistics. Models with similar F statistics were also compared with BIC.

RESULTS: Data from a sample of 253 participants (83% white, 66% male, mean age 47 years) with VAS/NRS pain intensity and PROMIS-PI scores at one or more timepoints were analyzed. The optimal classification for mild, moderate, and severe pain was CP 2,5 at baseline and 12-months. Although CP 3,6 had the highest F value at 6-months, there was not strong evidence to support CP 3,6 over CP 2,5 (BIC difference: 2.9); similarly, CP 3,7 had the highest value at 24-months, but the BIC difference over CP 2,5 was only 2.2.

CONCLUSIONS: VAS/NRS scores for pain among adults with burn injury can be categorized as mild (0-2), moderate (3-5), and severe (6-10). These findings advance our understanding regarding the meaning of pain intensity ratings after burn injury, and provide an objective definition for clinical management, quality improvement, and pain research.