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When Less is More for Rating Low-Back Impairment

Doctors need some way to measure impairment in back pain patients. Impairment is defined by the American Medical Association as "a loss of structure or function of part of the body." Doctors need a tool to measure: 1) the severity of the disorder; 2) when patients get better or worse; and 3) when it's safe to return to work.

In this study, researchers simplified a functional motion tool. The original model has five tests and takes too long (30 minutes). The new model measures the loss of function from a low back disorder using only one task (5 to 10 minutes).

The test was used first on healthy subjects. The subjects were adults of all ages and both sexes who did not have back pain. Then it was used on a group of 335 patients with low back pain. The results of each group were compared.

The authors report that the revised model has the same sensitivity as the original long test. Sensitivity of a test tells us how often the test shows a problem when, in fact, there is one. Specificity of the revised test went down slightly, from 94 to 92 percent. Specificity refers to how often a test shows no problem when there's no problem. In other words, the revised model of impairment rating is slightly more likely to say a healthy patient is impaired than the original model.

Using results from both tests, they also found the time to recovery was predicted the same in 90 percent of the patients. This means the revised model gave the same results as the original model nine out of 10 times. They conclude that the revised model with fewer tasks is excellent. Doctors and therapists can use it to rate impairment.

References: Sue A. Ferguson, PhD, and William S. Marras, PhD. Revised Protocol for the Kinematic Assessment of Impairment. In The Spine Journal March/April 2004. Vol. 4. No. 2. Pp. 163-169.

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