THE VISUAL ANALOG PAIN INTENSITY SCALE - WHAT IS MODERATE PAIN IN MILLIMETERS

One way to ensure adequate sensitivity for analgesic trials is to test the intervention on patients who have established pain of moderate to severe intensity. The usual criterion is at least moderate pain on a categorical pain intensity scale. When visual analogue scales (VAS) ar e the only pain measure in trials we need to know what point on a VAS represents moderate pain, so that these trials can be included in meta analysis when baseline pain of at least moderate intensity is an inclu sion criterion. To investigate this we used individual patient data fr om 1080 patients from randomised controlled trials of various analgesi cs. Baseline pain was measured using a 4-point categorical pain intens ity scale and a pain intensity VAS under identical conditions. The dis tribution of the VAS scores was examined for 736 patients reporting mo derate pain and for 344 reporting severe pain. The VAS scores correspo nding to moderate or severe pain were also examined by gender. Baselin e VAS scores recorded by patients reporting moderate pain were signifi cantly different from those of patients reporting severe pain. Of the patients reporting moderate pain 85% scored over 30 mm on the correspo nding VAS, with a mean score of 49 mm. For those reporting severe pain 85% scored over 54 mm with a mean score of 75 mm. There was no differ ence between the corresponding VAS scores of men and women. Our result s indicate that if a patient records a baseline VAS score in excess of 30 mm they would probably have recorded at least moderate pain on a 4 -point categorical scale. (C) 1997 International Association for the S tudy of Pain. Published by Elsevier Science B.V.