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Pain sensitivity as a correlate of clinical status in individuals with chronic low back pain.

STUDY DESIGN
A cross-sectional study of baseline correlates of clinical pain and functional status in consecutive patients being treated for chronic low back pain.


OBJECTIVES
To determine if an individual's global pain sensitivity, measured by experimental pain threshold to pressure at various regions of the body, is associated with baseline measures of clinical pain and physical functioning.


SUMMARY OF BACKGROUND DATA
Previous studies have demonstrated that in individuals with chronic low back pain, clinical pain and functional status are significantly associated with demographic, structural, and psychosocial factors. However, a large portion of variance remains unexplained. Because pain sensitivity (tenderness) has been shown to occur as a continuum in the population, the authors sought to determine if such sensitivity might be associated with clinical status in chronic low back pain, beyond what is known regarding demographic, structural, and psychosocial factors.


METHODS
Forty-five patients with chronic low back pain were assessed for a variety of demographic, structural, and psychosocial factors, which previously have been shown to contribute to clinical status. In addition, all patients underwent testing for pain tolerance and threshold at various areas of the body.


RESULTS
Age, degree of structural abnormality observed on magnetic resonance imaging, and depressive symptoms were all significantly correlated with either clinical pain or functional status. Pain sensitivity, the target of this investigation, accounted for significant proportions of variance in functional status and pain, even after controlling for demographic, structural, and psychosocial variables.


CONCLUSIONS
These pilot data suggest that an individual's experimental pain threshold (a measure of tenderness) is associated with baseline functional status and pain in cases of chronic low back pain and may represent an important domain warranting further investigation.