Email updates

Keep up to date with the latest news and content from BMC Musculoskeletal Disorders and BioMed Central.

Open Access Research article

Validation of the German version of the Neck Disability Index (NDI)

Holger Cramer1*, Romy Lauche1, Jost Langhorst1, Gustav J Dobos1 and Andreas Michalsen23

Author Affiliations

1 Department of Internal and Integrative Medicine, Kliniken Essen-Mitte, Faculty of Medicine, University of Duisburg-Essen, Am Deimelsberg 34a, 45276 Essen, Germany

2 Department of Internal and Integrative Medicine, Immanuel Hospital Berlin, Königstraße 63, 14109 Berlin, Germany

3 Institute for Social Medicine, Epidemiology, and Health Economics, Charité University Medical Center, Königstraße 63, 14109 Berlin, Germany

For all author emails, please log on.

BMC Musculoskeletal Disorders 2014, 15:91  doi:10.1186/1471-2474-15-91

Published: 19 March 2014

Abstract

Background

The Neck Disability Index (NDI) is the most commonly used outcome measure for neck pain. This study aimed to determine the psychometric properties of a German version of the NDI. Cross-cultural translation and psychometric testing of the NDI were performed.

Methods

The 10-item NDI was translated into German and administered to 558 patients with chronic unspecific neck pain (Mean age 49.9 ± 11.4 years, 76% female). The factor structure and reliability of the NDI were assessed using factor analysis, Cronbach’s alpha, split-half reliability (Spearman-Brown coefficient), and intra-class correlation (ICC2,1). To determine convergent validity, pain intensity (visual analog scale; VAS), pain on movement (VAS), and quality of life (Short Form 36 Health Survey Questionnaire; SF-36) were correlated with the NDI. Correlation with range of motion and sensitivity to change were also assessed in a subsample of 49 patients.

Results

The mean NDI score was 32.75 ± 13.09. Factor analysis revealed a single factor that explained 39.8% of the variance. Cronbach’s alpha was 0.81; Spearman-Brown coefficient was 0.80; and intra-class correlation was 0.81 (95% confidence interval = 0.78, 0.83). Significant correlations were found for pain intensity (r = 0.22, p < 0.01), pain on movement (r = 0.39, p < 0.01), quality of life (r = -0.30 to -0.45, p < 0.01), and range of motion (r = -0.34, p = 0.02). Patients who reported global improvement of health after an exercise or yoga intervention showed a higher decrease on the NDI than patients who reported no global improvement (p < 0.01).

Conclusions

The German version of the NDI has a comparable factor structure as the original version, acceptable psychometric properties, and is sensitive to change after physical activity. Neck disability is associated with other measures of neck pain.

Keywords:
Neck pain; Chronic pain; Disability; Neck disability index; Translation; German; Validity; Reliability; Factor structure; Sensitivity to change