RESUMEN
STUDY DESIGN: Cross-cultural adaptation and psychometric testing. OBJECTIVE: To perform a validated Russian translation and then to evaluate the validity and reliability of the Russian language version of the Neck Disability Index (NDI-RU). SUMMARY OF BACKGROUND DATA: Neck pain is highly prevalent and can greatly affect daily activity. The Neck Disability Index (NDI) is the most frequently used scale for self-rating of disability due to neck pain. Its translated versions are applied in many countries. However, the Russian language version of the NDI has not been developed yet. METHODS: Cross-cultural adaptation of the NDI-RU was performed according to established guidelines. Then, the NDI-RU was evaluated for content validity, concurrent criterion validity, internal consistency, test-retest reliability, factor structure, and minimum detectable change. RESULTS: Two hundred thirty-two patients took part in the study in total: 109 in validity (39.5 ± 10 yr), 123 in reliability (38.4 ± 11 yr; 80 in the test-retest phase). A culturally valid translation was achieved. NDI-RU total scores were distributed normally. Floor/ceiling effects were absent. Good values of Cronbach α were obtained for each item (from 0.80 to 0.84) and for the total NDI-RU (0.83). A 2-factor solution was found for the NDI-RU. The average interitem correlation coefficient was 0.53. Intraclass correlation coefficients for test-retest reliability coefficients ranged from 0.65 to 0.92 for different items and 0.91 for the total NDI-RU. Moderate correlation (Spearman rs = 0.62; P < 0.05) was found between the NDI-RU total score and graphic rating scalepain score. Completion of the NDI-RU takes 3.6 ± 1 minutes. CONCLUSION: The development of a Russian language version of the Neck Disability Index resulted in a valid, reliable instrument that can be used both in clinical practice and scientific investigations. LEVEL OF EVIDENCE: 1.
