An Outcome Measure of Functionality And Pain in Patients with Low Back Disorder: A Validation Iranian Version of The Core Outcome Measures Index (COMI)

Abstract

Background: Lumbar disc hernia (LDH) and lumbar spinal stenosis (LSS) are the most common diagnoses of low back and leg pain symptoms. The Core Outcome Measures Index (COMI) is a measure of health related quality of life in these patients. This study aimed to cross-culturally translate and validate the COMI in Iran.

Materials and Methods: This was a prospective clinical validation study. The translation and cross-cultural adaptation of the original questionnaire was 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 post-operative assessments (6 months follow-up). The Oswestry Disabiltiy Index (ODI) also was completed for patients. To test reliability the internal consistency was assessed by Cronbach's alpha coefficient and validity was assessed using convergent validity. Responsiveness to change also was assessed comparing patients’ pre- and postoperative scores.

Results: The Cronbach’s alpha coefficients for the COMI at preoperative and postoperative assessments ranged from 0.79 to 0.82 indicating a good internal consistency for the questionnaire. The change in the ODI after surgery was strongly correlated with change in the COMI, lending support to its good convergent validity (r = 0.78; 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).

Conclusions: In general, the Iranian version of COMI performed well and the findings suggest that it is a reliable and valid measure of back pain evaluation among LDH and LCS patients.