People with back pain don't always agree on what improvements suggest they are better. Is a 10 per cent decrease in pain enough to say, I'm better now? How much improvement in function suggests that treatment is working well?
In this study, researchers attempt to find the minimal important change (MIC) for five commonly used questionnaires for back pain patients. The Visual Analogue Scale, Numerical Rating Scale, Roland Disability Questionnaire, Oswestry Disability Index, and the Quebec Back Pain Disability Questionnaire were included.
These surveys measure pain, function, work disability, health status, and patient satisfaction. Two outcomes of particular interest in this study were pain and back specific function.
The researchers asked a panel of experts two questions: How much change in the scores for these tests before and after treatment is meaningful? If the outcomes are statistically significant, are they also clinically meaningful? In other words, if the improvement in test scores signifies an important change, does this match up with the patient's level of pain and function?
After much discussion, a consensus of opinion was reached. The panel agreed that the MIC for the questionnaires included in this study was a 30 per cent improvement. The same measure was used for all patients whether in the acute, subacute, or chronic phase of back pain.
Doctors and therapists working with back pain patients can use this 30 per cent figure as a baseline for judging outcomes. MIC values can still depend on each patient's circumstances.
Each case should be judged carefully for evidence that the MIC value fits the patient. For example, a different MIC may be needed for children versus adults. Likewise, surgical versus nonsurgical cases may require different percentages.
The authors report that the proposed 30 per cent MIC is a guideline, not a standard for failure or success of treatment. If all researchers have a common starting point, then the results of their research can be compared and contrasted to other studies using the same test measures.
For now, this value is suggested for use with individuals, not groups of people. Further research is needed to verify this figure for the baseline. Changes may be needed based on future study results.
Raymond W. J. G. Ostelo, PhD, et al. Interpreting Change Scores for Pain and Functional Status in Low Back Pain. In Spine. January 2008. Vol. 33. No. 1. Pp. 90-94.
