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