A clinical comparison of two pain scales: Correlation, remembering chronic pain and a measure of compliance

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Abstract
Chronic pain patients (15) rated their pain intensity on both a visual analog scale and a verbal scale so that comparisons between the scales could be made for each subject. Compliance to fill in the rating blanks and the remembering of pain intensity were also studied. Subjects first made a pre-baseline estimate of their pain and then they rated their pain throughout a baseline and treatment period averaging 5 wk. Four to 9 wk after baseline, subjects were asked to remember how much pain they had at baseline and to confidentially provide ratings concerning their compliance. Results indicated that 2/3 of the individual subjects had significant correlations between the scales with a mean of 0.68. The 1/3 of the subjects who did not have significant correlations also had significantly less variability in their ratings than did subjects with significant correlations. This low level of variability may account for the lack of a significant correlation between the scales for these subjects. Discrepancies between actual baseline and remembered pain ratings were observed on both rating scales, but the visual analog scale produced significantly greater discrepancies than the verbal scale. This was mainly because subjects tended to overestimate their baseline pain on the visual analog scale, while discrepancies on the verbal scale were in both directions (overestimations, underestimations) when taken as a group. Discrepancies between the pre-baseline estimate of pain and remembered ratings were smaller than the discrepancy between actual baseline ratings and remembered pain ratings suggesting that there is an important cognitive component guiding the remembered pain recordings. Compliance to fill in the blanks at the scheduled time was high on both scales. The results imply that the verbal pain scale may be the scale of choice when compared to the visual analog scale.