Cross-cultural adaptation and validation of the Dutch version of the core outcome measures index for low back pain

The core outcome measures index (COMI) is a validated multidimensional instrument for assessing patient-reported outcome in patients with back problems. The aim of the present study is to translate the COMI into Dutch and validate it for use in native Dutch speakers with low back pain. The COMI was translated into Dutch following established guidelines and avoiding region-specific terminology. A total of 89 Dutch-speaking patients with low back pain were recruited from 8 centers, located in the Dutch-speaking part of Belgium. Patients completed a questionnaire booklet including the validated Dutch version of the Roland Morris disability questionnaire, EQ-5D, the WHOQoL-Bref, the Numeric Rating Scale (NRS) for pain, and the Dutch translation of the COMI. Two weeks later, patients completed the Dutch COMI translation again, with a transition scale assessing changes in their condition. The patterns of correlations between the individual COMI items and the validated reference questionnaires were comparable to those reported for other validated language versions of the COMI. The intraclass correlation for the COMI summary score was 0.90 (95% CI 0.84–0.94). It was 0.75 and 0.70 for the back and leg pain score, respectively. The minimum detectable change for the COMI summary score was 1.74. No significant differences were observed between repeated scores of individual COMI items or for the summary score. The reproducibility of the Dutch translation of the COMI is comparable to that of other validated spine outcome measures. The COMI items correlate well with the established item-specific scores. The Dutch translation of the COMI, validated by this work, is a reliable and valuable tool for spine centers treating Dutch-speaking patients and can be used in registries and outcome studies.