Pain relief scale is more highly correlated with numerical rating scale than with visual analogue scale in chronic pain patients

The pain relief scale (PRS) is a method that measures the magnitude of change in pain intensity after treatment. The present study aimed to evaluate the correlation between PRS and changes in pain determined by the visual analogue scale (VAS) and numerical rating scale (NRS), to confirm the evidence supporting the use of PRS. Sixty patients with chronic spinal pain that had a VAS and NRS recorded during an initial examination were enrolled in the study. One week later, the patients received an epidural nerve block, then VAS, NRS, and PRS assessments were performed. Differences between VAS and NRS were compared to the PRS and scatter plots and correlation coefficient were generated. The differences and magnitude of decrease in the VAS and NRS raw data were converted to percentile values, and compared to the PRS. Both VAS and NRS values exhibited strong correlations (> 0.8) with PRS. Further, the differences between the VAS-PRS R (0.859) and NRS-PRS R (0.915) were statistically significant, (P = 0.0259). Compared to PRS, the VAS and NRS percentile scores exhibited higher correlation coefficients than scores based on the raw data differences. Furthermore, even when converted to a percentile, the NRS%-PRS R (0.968) was higher than the VAS%-PRS R (0.904), P = 0.0001. The results indicated that using the PRS together with NRS in pain assessment increased the objectivity of the assessment compared to using only VAS or NRS, and may have offset the limitations of VAS or NRS alone.