Psychomotor speed in chronic low-back pain patients and healthy controls: construct validity and clinical significance of the measure.

The effect of ethanol on reaction times was studied in 5 healthy men to test the construct validity of the measure. Reaction times were studied among 61 healthy controls and 99 patients with chronic low-back pain (68 moderate and 31 severe) to evaluate the diagnostic value of reaction time measurements. Analysis of receiver operating characteristics was used to calculate the discriminative power of the reaction time measurements. The severity of low-back pain was associated with slow reaction times but the diagnostic value of a single reaction time measurement was low due to insufficient sensitivity. In conclusion, even though many patients with low-back pain suffer from central impairment of motor function, a single reaction time measurement is not usable in evaluation of the severity of low-back pain.