Cross-cultural adaptation and validation of the Arabic version of the Core Outcome Measures Index for the back (COMI-back) in patients with non-specific low back pain

Purpose To cross-culturally adapt the Core Outcome Measures Index for the back (COMI-back) for the Arabic language and to test its reliability and validity in Egyptian patients with non-specific low back pain (LBP). Methods COMI-back was translated and cross-culturally adapted into Arabic according to standard guidelines. Its construct validity was assessed in 85 patients with chronic LBP (mean (+/- SD) age, 41.1 (+/- 10.4) years and 65/85 (76.5%) female) who completed a booklet of questionnaires including the Arabic versions of COMI-back, Roland Morris disability questionnaire, Oswestry disability index, the short form health survey 36, and the visual analogue scale for back pain. Test-retest reliability was assessed in 52 participants who completed the booklet again within 7 days. Results Floor effects (worst status; 1.2-10.6%) and ceiling effects (best status; 1.2-11.8%) for COMI-back were acceptable, except for symptom-specific well-being (18.8%, floor), leg pain (23.5%, ceiling), and work disability (31.8%, ceiling). The COMI item scores correlated with those of the reference questionnaires (rho = 0.45-0.88) to the hypothesized extent, except for the COMI symptom-specific well-being (rho = 0.16-0.17) and quality of life (rho = 0.38). The intra-class correlation coefficient for the summary score was 0.90, whereas that of the individual items ranged from 0.71-0.92. The standard error of measurement and minimal detectable change for the summary score were 0.51 and 1.41 points, respectively. The predefined hypotheses for construct validity and reliability were largely confirmed. Conclusion The Arabic version of COMI-back represents a valid and reliable instrument for use in Arabic-speaking patients with non-specific LBP.