Cross-cultural adaptation and validation of the Traditional Chinese version of the Core Outcome Measures Index in patients with low back pain

Purpose This study aimed to carry out a cross-cultural adaptation of the Core Outcome Measures Index (COMI) for use in Traditional Chinese-speaking patients with low back pain (LBP) and to investigate its psychometric properties. Methods A total of 224 patients with LBP > 6 weeks who visited our spine center from May 2018 to May 2019 were included in the study. Patients completed a booklet of questionnaires including the following: (1) pain Numeric Rating Scale, (2) Oswestry Disability Index, (3) Roland–Morris Disability Questionnaire, (4) EuroQol-five dimension (EQ-5D), and (5) COMI. Patients were sent a second booklet (also containing a transition question to indicate any change in condition) to be completed again within one month after the first. Fifty-two patients did not receive any intervening treatment (group 1), while the other 172 patients received medical treatment (group 2) between the two questionnaires. Results The intraclass correlation coefficient (ICC) for the COMI summary score was 0.94 (95% CI 0.89–0.97); the standard error of measurement (SEM) was 0.41 and the minimum detectable change (MDC) score was 1.14. The COMI summary scores showed a low floor effect (1.8%) and ceiling effect (0.4%). All COMI item scores demonstrated the hypothesized correlations with their corresponding full-length questionnaires except for the pain item (correlation stronger than hypothesized). Standardized response means (SRM) for the COMI items in the treated group were between 0.58 and 1.30. Regarding the ability of the COMI change score to differentiate between good and poor outcomes, the area under the receiver operating characteristic (AUROC) curve was 0.77 [standard error (SE) 0.07, 95% confidence interval (CI) 0.68–0.84] and the minimal clinically important change (MCIC) score was ≥ 1.85 points. Conclusion The Traditional Chinese COMI represents a practical and reliable tool for the assessment of Traditional Chinese-speaking patients with back problems.