The visual analogue thermometer and the graphic numeric rating scale: A comparison of self-report instruments for pain measurement in adults with burns

To evaluate the adequacy of pain management in burn care, pain measurement is essential. The visual analogue thermometer (VAT) and graphic numeric rating scale (GNRS) are frequently used self-report instruments for burn pain. To legitimise their interchangeable use in research and practice, we aimed to compare self-reports obtained by the VAT and GNRS, the ability of the scales to differentiate background from procedural pain, and to compare potential cutpoints. Adults with acute burns (N = 319) participated in the study (67% male, mean age 40.3 years (SD 16), mean TBSA 9.9% (SD 10.4). Correlation coefficients between VAT and GNRS were 0.64 and 0.55 for, respectively, morning and afternoon background pain and 0.51 for procedural pain (p < 0.01). VAT scores were lower than GNRS scores for all pain types (p < 0.01). Both scales could differentiate background from procedural pain: procedural pain was higher (p < 0.01). The standardized response mean was moderate (0.518 for VAT and 0.571 for GNRS). Self-reported thresholds for 'unacceptable pain' by GNRS were higher than by VAT (p < 0.001). ROC analyses showed that the highest sensitivity was reached for pain score 2 for both scales. The results suggest that the instruments cannot be used interchangeably without taking their differences into account.