Development and preliminary psychometric testing of the centrality of pain scale

The objective of the study was to develop and begin to evaluate a new measure of the centrality of pain in patients' lives.

The study was designed as a cross-sectional survey and cognitive interviews.

The study was set in an academic general internal medicine clinic.

Sixty-five adult internal medicine patients with chronic nonmalignant pain (CNMP) participated in the study.

We assessed content validity and clarity of the 10-item Centrality of Pain Scale (COPS) by soliciting feedback from chronic pain experts and by conducting cognitive interviews with patients with CNMP. We assessed internal consistency reliability using Cronbach's alpha. We assessed construct validity by comparing the COPS with other measures of chronic pain morbidity including pain severity, depression, anxiety, physical and mental health function, posttraumatic stress disorder, quality of life, and provider assessment.

Health care providers felt the COPS had excellent face validity. Cognitive interviews revealed that patients' understanding of the items matched the intended construct, the scale measured an important concept, and items were easy to understand. The COPS had excellent internal consistency (alpha = 0.9). It was negatively associated with age (r = -0.29; P = 0.02), but not with other demographic characteristics. Higher COPS scores were associated with poorer physical (r = -0.48; P < 0.001) and mental (r = -0.39; P = 0.002) health function, quality of life (r = -0.36; P = 0.004), and provider assessment of stability (r = -0.38; P = 0.004) as well as with greater pain grade (r = 0.55; P < 0.001), and depression (r = 0.63; P < 0.001). In multivariate analyses, age, physical and mental health function, and depression were independently associated with COPS.

The COPS has excellent internal consistency and construct validity. Additional studies are needed to further validate the scale.