A comparison of cognitive measures in low back pain: statistical structure and clinical validity at initial assessment.

Four cognitive measures--MHLC, PLC, CSQ and PRSS/PRCS--were directly compared in 120 U.K. patients with chronic low back pain. 80% of the individual items in the PLC and 86% in the CSQ had satisfactory test-retest reliability, as had most of the scales of the CSQ and the PLC PC scale. The items and the scales of the MHLC and the PRSS/PRCS had lower reliability. The factor structures of the PLC and the PRSS/PRCS bore close similarity to the original descriptions. The CSQ structure was similar to the original but further investigation of its psychometric properties is required. The structure of the MHLC was not replicated. Considerable communality was found between the cognitive measures. The strongest relationship found in this study was between the CSQ and PRSS catastrophising scales and depressive symptoms. There was also a relationship among cognitive measures and both disability and work loss which persisted even after controlling for severity of pain and depressive symptoms. The present results suggest that the concept of catastrophising has greatest potential for understanding current low back symptoms and that the CSQ may be the most useful measure of this. Other work, however, suggests that the PLC may also be of value in following change and predicting response to treatment.