Rasch analysis supports the use of the depression, anxiety, and stress scales to measure mood in groups but not in individuals with chronic low back pain.

OBJECTIVE: Chronic pain is a common problem that is associated with mood disorders such as depression. The Depression, Anxiety, and Stress Scales (DASS-21) questionnaire is commonly used to help measure disordered mood. In this study, we used Rasch analysis to analyze the clinimetric properties of the DASS-21 in a chronic low back pain sample. STUDY DESIGN AND SETTING: A Rasch analysis was conducted on data collected as a part of a randomized hospital-based placebo-controlled trial. DASS-21 questionnaires were completed by the 154 enrolled participants. RESULTS: The DASS-21 subscales fit the Rasch model. No differential item functioning was detected for age, gender, pain severity, or disability. Reliability for individual use was supported for the depression subscale (Person Separation Index [PSI]=0.86) but group use only for the anxiety (PSI=0.74) and stress (PSI=0.82) subscales. A DASS-21 aggregate score of "negative affect" lacked fit to the Rasch model (χ(2)=191.48, P<0.001). CONCLUSION: This is the first study that used Rasch analysis to demonstrate that the DASS-21 subscales demonstrate adequate measurement properties for research involving groups with chronic pain. Only the DASS-21 depression subscale demonstrated adequate reliability for use with individuals with chronic pain. The use of a single DASS-21 aggregate score as a measure of "negative affect" was not supported.

Cortical changes in chronic low back pain: current state of the art and implications for clinical practice.

There is increasing evidence that chronic pain problems are characterised by alterations in brain structure and function. Chronic back pain is no exception. There is a growing sentiment, with accompanying theory, that these brain changes contribute to chronic back pain, although empirical support is lacking. This paper reviews the structural and functional changes of the brain that have been observed in people with chronic back pain. We cast light on the clinical implications of these changes and the possibilities for new treatments but we also advise caution against concluding their efficacy in the absence of solid evidence to this effect.

Self-reported assessment of disability and performance-based assessment of disability are influenced by different patient characteristics in acute low back pain.

For an individual, the functional consequences of an episode of low back pain is a key measure of their clinical status. Self-reported disability measures are commonly used to capture this component of the back pain experience. In non-acute low back pain there is some uncertainty of the validity of this approach. It appears that self-reported assessment of disability and direct measurements of functional status are only moderately related. In this cross-sectional study, we investigated this relationship in a sample of 94 acute low back pain patients. Both self-reported disability and a performance-based assessment of disability were assessed, along with extensive profiling of patient characteristics. Scale consistency of the performance-based assessment was investigated using Cronbach's alpha, the relationship between self-reported and performance-based assessment of disability was investigated using Pearson's correlation. The relationship between clinical profile and each of the disability measures were examined using Pearson's correlations and multivariate linear regression. Our results demonstrate that the battery of tests used are internally reliable (Cronbach's alpha = 0.86). We found only moderate correlations between the two disability measures (r = 0.471, p < 0.001). Self-reported disability was significantly correlated with symptom distribution, medication use, physical well-being, pain intensity, depression, somatic distress and anxiety. The only significant correlations with the performance-based measure were symptom distribution, physical well-being and pain intensity. In the multivariate analyses no psychological measure made a significant unique contribution to the prediction of the performance-based measure, whereas depression made a unique contribution to the prediction of the self-reported measure. Our results suggest that self-reported and performance-based assessments of disability are influenced by different patient characteristics. In particular, it appears self-reported measures of disability are more influenced by the patient's psychological status than performance-based measures of disability.