Do Measures of Pain Measure Up? Visual Analog Scales for Low Back PainIf you see a doctor for low back pain, he or she may ask you to look at a scale from zero (no pain at all) to 100 (the worst pain imaginable) and point to the place that best describes your pain. This is called a "visual analog scale," or VAS. Doctors often use VAS to measure the intensity of patients' pain. This helps doctors suggest appropriate treatment. They also use VAS after surgery, to see whether pain has gone down.
Though VAS is popular, there are still questions about how to use it and exactly what it measures. Are pain scores from VAS related to other measures of patient outcomes, such as use of painkillers and patient satisfaction?
Seven hundred fifty-five patients had surgery for low back pain. Patients ranged in age from 15 to 86, with an average of 50. There were slightly more men than women.
Before surgery and four and 12 months after, patients rated their back and leg pain using VAS. Use of painkillers was also recorded. After surgery, patients were asked whether their back and leg pain had changed, and whether they were satisfied with their results.
Before surgery, patients with different diagnoses showed distinct patterns of pain. The authors were surprised just how clear-cut these patterns were. Patients with herniated discs (roughly half of the patients) had minor back pain but strong leg pain. Patients who had narrowing inside the spinal canal had moderate back pain and strong leg pain. Patients whose vertebra had dislodged and slid forward had moderate back pain and minor leg pain. Patients who had degenerative disc disease had the most back pain of any group, along with minor leg pain.
Pain improved by the four-month follow-up for all of these conditions. Twelve months after surgery, patient satisfaction was related to all of the pain measures in this study (VAS pain scores, the change-in-pain question, and use of painkillers). Notably, patient satisfaction was the most closely related to VAS scores after surgery and direct questions about changes in pain. This suggests that comparing before-and-after pain scores from VAS may not be the best way to measure patients' results. It may be preferable to examine VAS scores after surgery alone or to simply ask patients about changes in pain.
So what's the best bet for gauging patients' results from surgery? The authors can't say. They're not even sure this "best bet" question is the right one to ask. Though measures of pain are related to each other, each measures something slightly different. Certainly, the way pain is measured matters. It's important to keep this in mind when comparing treatment results that are described in terms of changes in pain.
Gustavo Zanoli, MD, BjÃ¶rn StrÃ¶mqvist, MD, PhD, and Bo JÃ¶nsson, MD, PhD. Visual Analog Scales for Interpretation of Back and Leg Pain Intensity in Patients Operated for Degenerative Lumbar Spine Disorders. In Spine. October 1, 2001. Vol. 26. No. 21. Pp. 2375-2380.
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