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 Gottingen/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. (C) 2010 European Federation of International Association for the Study of Pain Chapters. Published by Elsevier Ltd. All rights reserved.