Psychometric evaluation of the PainCAS Interference with Daily Activities, Psychological/Emotional Distress, and Pain scales.

PURPOSE: The PainCAS is a web-based clinical tool for assessing and tracking pain and opioid risk in chronic pain patients. Despite evidence for its utility within the clinical setting, the PainCAS scales have never been subject to psychometric evaluation. The current study is the first to evaluate the psychometric properties of the PainCAS Interference with Daily Activities, Psychological/Emotional Distress, and Pain scales.

METHODS: Patients (N = 4797) from treatment centers and hospitals in 16 different states completed the PainCAS as part of routine clinical assessment. A subsample (n = 73) from two hospital-based treatment centers also completed comparator measures. Rasch Rating Scale Models were employed to evaluate the Interference with Daily Activities and Psychological/Emotional Distress scales, and empirical evaluation included assessment of dimensionality, discrimination, item fit, reliability, information, and person-to-item targeting. Additionally, convergent and discriminant validity were evaluated through classical test theory approaches. Convergent validity of the Pain scales was evaluated through correlations with corresponding comparator items.

RESULTS: One Interference with Daily Activities item was removed due to poor functioning and discrimination. The retained items from the Interference with Daily Activities and Psychological/Emotional Distress scales conformed to unidimensional Rasch measurement models, yielding satisfactory item fit, reliability, precision, and coverage. Further, results provided support for the convergent and discriminant validity of these two scales. Convergent validity between the PainCAS Pain and BPI Pain items was also strong.

CONCLUSION: Taken together, results provide strong psychometric support for these PainCAS Pain scales. Strengths and limitations of the current study are discussed.