Reliability and validity of the Polish version of the Core Outcome Measures Index for the neck

Purpose Patient reported outcome measures play an increasingly important role in the outcomes research. The Core Outcome Measures Index (COMI) is a short, multidimensional instrument initially developed for the use by patients with low back pain. This study is an evaluation of a Polish version of COMI adapted for neck pain. Methods One hundred twenty-three patients complaining of neck pain were enrolled. All of them completed a questionnaire booklet containing COMI-neck, Neck Disability Index and Likert-type questions regarding the frequency of use of pain medications and pain frequency. Ninety-eight patients returned the retest questionnaire. Data quality was also assessed. Assessment of psychometric properties included examination of data quality, construct validity, test–retest reliability and factor analysis. Results The quality of data was good with no missing answers and a little floor effect. Exploratory factor analysis revealed a single-factor structure. Reliability expressed as intraclass correlation coefficient was 0.88 (95 % CI 0.84–0.92) for the overall COMI score and was generally good for most of individual core items. The minimum detectable change (MDC 95% ) was 1.97. Conclusion This version of the COMI-neck is a valid and reliable instrument, with good psychometric properties. It can be recommended for Polish-speaking patients.