Validation of the Simplified Chinese version of the Core Outcome Measures Index (COMI).

PURPOSE: To translate the Core Outcome Measures Index (COMI) into Simplified Chinese and then validate it for Mainland Chinese patients with low back pain (LBP).

METHODS: A total of 120 consecutive patients with LBP >3 months who visited our outpatient clinic from December 2011 to March 2012 were asked to complete a questionnaire booklet including the following: (1) the Roland Morris disability questionnaire (RMQ) (Fan et al. in Spine 37(10):875-880, 2012), (2) the Short Form Health Survey (SF-36) (Zhang et al. in Int J Med Sci 9(7):521-526, 2012), (3) the Oswestry Disability Index (ODI) (Liu et al. in Spine 34(11):1211-1216, 2009), (4) visual analogue scale (VAS) measure of pain, and (5) COMI. These patients were also asked to complete a second COMI questionnaire and a transition questionnaire (5-point Likert scale: better, a little better, no change, a little worse, worse) and to return the second COMI questionnaire via mail within 1 month.

RESULTS: The floor effects for the COMI items ranged from 5.8 to 12.5 %. High values (28.3, 27.5, and 25.8 %, respectively) were found for symptom-specific quality of life, social disability, and work disability. Regarding the ceiling effects, the social and work disabilities were relatively high at 17.5 and 24.2 %, respectively. For other items, the values ranged from 0 to 14.2 %. Neither floor nor ceiling effects were found for the COMI summary score. Excellent correlations were found between the COMI pain scores and VAS scores (Rho = 0.89) and between the COMI pain and the SF-36 bodily pain domain (Rho = 0.84). Other individual items and summary scores showed a very good correlation (Rho = 0.54-0.72) with the corresponding questionnaires except for "symptom-specific well-being" (0.31-0.45). One-way repeated measures ANOVA was used to determine the intraclass correlation coefficient (ICC). The ICC for the entire COMI score was 0.91 (95 % CI 0.85-0.94) and 0.81-0.86 for the two pain scores (back and leg). The "minimum detectable change'' (MDC 95 %) for the COMI summary score was 1.91 points. No significant difference in the mean values was found for the repeated scores of individual items or the summary score.

CONCLUSION: The Simplified Chinese version of COMI showed satisfactory reliability and good psychometric properties. This concise questionnaire is suitable for widespread use in Mainland China.