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 intensityafter treatment. The present study aimed to evaluate the correlation between PRS and changesin pain determined by the visual analogue scale (VAS) and numerical rating scale (NRS), toconfirm the evidence supporting the use of PRS. Sixty patients with chronic spinal pain that hada VAS and NRS recorded during an initial examination were enrolled in the study. One weeklater, the patients received an epidural nerve block, then VAS, NRS, and PRS assessments wereperformed. Differences between VAS and NRS were compared to the PRS and scatter plots andcorrelation coefficient were generated. The differences and magnitude of decrease in the VASand NRS raw data were converted to percentile values, and compared to the PRS. Both VAS andNRS values exhibited strong correlations (> 0.8) with PRS. Further, the differences between theVAS-PRS R (0.859) and NRS-PRS R (0.915) were statistically significant, (P = 0.0259). Comparedto PRS, the VAS and NRS percentile scores exhibited higher correlation coefficients thanscores 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 resultsindicated that using the PRS together with NRS in pain assessment increased the objectivity ofthe assessment compared to using only VAS or NRS, and may have offset the limitations ofVAS or NRS alone.Key words: Pain relief scale, numerical rating scale, visual analogue scale, pain measurement,pain intensity measurement, pain intensity scale