An outcome measure of functionality and pain in patients with low back disorder: A validation study of the Iranian version of Core Outcome Measures Index

BACKGROUND: Lumbar Disc Herniation (LDH) and Lumbar Spinal Stenosis (LSS) are the most common diagnoses of low back and leg pain symptoms. This study aimed to cross-culturally translate, and validate the Core Outcome Measures Index (COMI) in Iran. METHODS: The translation and cross-cultural adaptation of the original questionnaire were performed in accordance with published guidelines. A total of 121 patients with LDH or LSS were asked to respond to the questionnaire at two points in time: Pre and postoperative assessments (6 months follow-up). The Oswestry Disability Index (ODI) also was completed. To test the reliability, the internal consistency was assessed by Cronbach's alpha coefficient, and validity was assessed using convergent validity. Responsiveness to change also was assessed for comparing patients’ pre and postoperative scores. RESULTS: The Cronbach's alpha coefficients for the COMI at pre and postoperative assessments ranged from 0.79 to 0.82, indicating a good internal consistency. The change in the ODI after surgery was strongly correlated with change in the COMI, lending support to its good convergent validity (r = 0.79 for LDH and r = 0.77 for LSS; P < 0.001). In addition, the correlation of each item with its hypothesized subscale of the COMI showed satisfactory results suggesting, that the items had a substantial association with the subscale, representing the concept. Further analysis also indicated that the questionnaire was responsive to change (P < 0.0001). CONCLUSION: The Iranian version of COMI performed well, and the findings suggest that it is a reliable and valid measure of back pain treatment evaluation among LDH and lumbar canal stenosis patients.