Neck Pain and Disability Scale and the Neck Disability Index: reproducibility of the Dutch Language Versions

The first aim of this study was to translate the Neck Pain and Disability Scale (NPAD) from English into Dutch producing the NPAD-Dutch Language Version (DLV). The second aim was to analyze test-retest reliability and agreement of the NPAD-DLV and the Neck Disability Index (NDI)-DLV. The NPAD was translated according to established guidelines. Thirty-four patients (mean age 37.5 years, 68% female) with chronic neck pain (CNP), within an outpatient rehabilitation setting, participated in this study. The NPAD-DLV and the NDI-DLV were filled out twice with a mean test-retest interval of 18 days. The intraclass correlation coefficient of the NPAD-DLV was 0.76 (95% confidence interval (CI) 0.57-0.87) and of the NDI-DLV 0.84 (95% CI 0.69-0.92). The limits of agreement of the NPAD-DLV and the NDI-DLV were, respectively, +/- 20.9 (scale 0-100) and +/- 6.5 (scale 0-50). The reliability of the NPAD-DLV and the NDI-DLV was acceptable for patients with CNP. The variation ('instability') in the NPAD-DLV total scores was relatively large and larger than the variation of the NDI-DLV