Development of a severity discrimination scale based on physical quality of life for patients with chronic pain

Deterioration of quality of life in patients with chronic pain is difficult to treat. Chronic pain in patients with low quality of life may be "severe" and require multidisciplinary treatments. This study aimed to develop an objective severity discrimination scale based on quality of life measurements to identify patients with "severely disabling" chronic pain.

Subjects were 156 patients with chronic pain whose numerical rating pain score was ≥1 and who had pain for ≥3 months. Diseases associated with chronic pain included spinal diseases, joint diseases, concomitant diseases, complex regional pain syndromes, and other musculoskeletal diseases. Patients were divided into low, middle, and high groups based on physical quality of life summary scores on the Short Form-36. The mental component summary, painDETECT, Japanese version of the Pain Catastrophizing Scale, Brief Scale for Psychiatric Problems in Orthopaedic Patients, and factors related to degree/quality of pain during the past 4 weeks were analyzed to identify components in the low group. The score weighting factor for discriminating between the high and low groups was determined by discriminant analysis.

Factor analysis identified 4 factors representing features of chronic pain patients with low QOL: enhanced perception of pain, pain catastrophic thoughts, depressive sleep disorder, and pain intensity. For discriminant analysis, patients were defined as those with low physical quality of life if each factor's total score multiplied by a factor plus a constant value of 2.6 was ≥0, and high quality of life if it was <0. The receiver operating characteristic curve area used to determine the cut-off value was 0.71, with 67.3% sensitivity and specificity.

We developed a 33-question severity discrimination scale to define "severely disabling" chronic pain based on physical quality of life. "Severely disabling" patients identified on this scale could represent chronic pain patients needing focused multidisciplinary treatment.