title: Development of a short version of the Neck Pain and Disability Scale.
abstract: Previous evaluations of the 20-item Neck Pain and Disability Scale (NPAD) were indicative of excessive redundancy of the measure. The aim of this study was to develop a shortened version of the NPAD (sf-NPAD) based on results of item-to-total-score correlations and factor analysis as published by the developers of the original NPAD. Two items with the highest item-to-total score correlation were selected per factor subscale with the exception of one factor consisting of only one item. This resulted in the selection of 9 items for the sf-NPAD. The sf-NPAD was validated in a separate sample of 448 neck pain patients from 15 general practices in the area of Göttingen/Germany. Participants completed the 20-item NPAD German version and gave additional sociodemographic and clinical information. Psychometric properties of the sf-NPAD were evaluated using Cronbach's alpha, item-to-total-score correlation, and unrestricted principal factor analysis. Construct validity was evaluated by Pearson's r with clinical characteristics. Discriminative validity was examined by comparing differences between subgroups stratified by psychosocial characteristics using t-tests for mean scores. Cronbach's alpha of the sf-NPAD was 0.88. Item-to-total-scale correlations ranged between 0.628 and 0.815, and sf-NPAD items homogeneously loaded on a single factor. Correlation analysis showed high correlations with criterion variables. The sf-NPAD scores of patient subgroups were significantly different showing good discriminative validity. In conclusion, the sf-NPAD demonstrated good validity and internal consistency in this general practice setting. The abbreviated version may facilitate applicability of the scale in clinical and research settings.
authors.affiliation: Department of General Practice and Family Medicine, University of Göttingen, Humboldtallee Göttingen, Germany. eblozik@gwdg.de
authors.forename: Eva
authors.initials: E
authors.lastname: Blozik
authors.forename: Michael M
authors.initials: MM
authors.lastname: Kochen
authors.forename: Christoph
authors.initials: C
authors.lastname: Herrmann-Lingen
authors.forename: Martin
authors.initials: M
authors.lastname: Scherer
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D004185:Disability Evaluation; D005163:Factor Analysis, Statistical; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D019547:Neck Pain / Q000503:physiopathology*; D010147:Pain Measurement; D011594:Psychometrics; D015203:Reproducibility of Results; D011795:Surveys and Questionnaires