Validity, internal consistency and self-rated change of the patient enablement instrument in patients with chronic musculoskeletal pain

Abstract

Objective: Patient enablement reflects patient’s understanding of and coping with illness. The aim of this study was to investigate the content validity, construct validity, internal consistency and self-rated change (SRC) of the Patient Enablement Instrument (PEI) in patients with whiplash-associated disorders, cervical radiculopathy and mixed chronic pain treated in different settings. Design: Psychometric analyses. Participants: Patients with disabling non-malignant chronic musculoskeletal pain. Methods: Participants answered questionnaires on disability (Neck Disability Index (NDI) or Functional Rating Index (FRI)), anxiety/depression (Hospital Anxiety and Depression Scale; HADS) and general health (EuroQol; EQ-5D). Content validity, construct validity (confirmatory factor analysis), internal consistency and cut-off for SRC were investigated for the PEI after treatment. The SRC value was the receiver operating characteristic (ROC) curve optimal cut-off point. Results: After treatment all items were completed by 516 patients (mean standard deviation (SD) age 45.1 years (SD 10.1), women 75% (n=385)). The 1-factor PEI model had approximate fit to the data. The internal consistency Cronbach’s alpha was between 0.878 and 0.929 for the 3 groups. Correlations between the PEI and the NDI/FRI, HADS and EQ-5D were fair to good. The SRCROC for whiplash-associated disorders, cervical radiculopathy and mixed chronic pain groups was 5, 6 and 4 points in the PEI, respectively. Conclusion: The PEI showed fair content validity, construct validity and internal consistency. However, the scale needs further development to improve measurement of change.