The incremental validity of lumbar surface EMG, behavioral observation, and a symptom checklist in the assessment of patients with chronic low-back pain.

This study evaluated the comparative ability of lumbar surface EMG, behavioral observation, and a symptom checklist to correctly classify three groups of participants, (1) 18 patients with chronic low-back pain (CLBP), demonstrating excessive and/or anatomically inconsistent motor, sensory, and tenderness responses during a neurological examination, (2) 33 patients with CLBP exhibiting few or no inconsistent responses, and (3) 30 healthy matched controls. Discriminant analyses were used to develop predictive models. Correct classification rates for the individual assessments and all combinations of assessments were contrasted. Each modality predicted group membership significantly better than weighted chance (23%), with the symptom checklist approach having the highest individual correct classification rate (64%). The best combination of modalities was the symptom checklist and lumbar surface EMG (70% correct classification rate). The sensitivity and specificity of the individual assessments and all combinations of assessments are also presented.