PurposeTo investigate the validity of the Neck Pain and Disability Scale Dutch Language Version (NPAD-DLV) and the Neck Disability Index (NDI)-DLV.MethodsNPAD–DLV, NDI–DLV, Short-Form-36 Health Survey (SF-36)-DLV, visual analog scale (VAS)pain and VASdisability were administered to 112 patients with non-specific chronic neck pain in an outpatient tertiary rehabilitation setting. Twenty seven hypotheses were formulated regarding validity. NPAD–DLV and NDI–DLV were evaluated for content validity (normal distribution total scores, missing items, floor and ceiling effects), internal consistency (Cronbach’s alpha and Spearman Item–total correlations), construct validity (Pearson correlations with SF-36 domains, VASpain and VASdisability and Pearson correlation between total scores of NPAD–DLV and NDI–DLV).ResultsNPAD–DLV and NDI–DLV scores were distributed normally. Missing items were negligible. Floor and ceiling effects were absent in NPAD–DLV and in NDI–DLV two items had floor effects and one item had a ceiling effect. Cronbach’s alpha of NPAD–DLV was 0.93 and of NDI–DLV 0.83. Item–total correlations ranged for NPAD–DLV from 0.45 to 0.73 and for NDI–DLV from 0.40 to 0.64. The correlation between, respectively, NPAD–DLV and NDI–DLV and: SF-36 domains ranged from −0.36 to −0.70 and from −0.34 to −0.63; VASpain was 0.54 and 0.43; VASdisability was 0.57 and 0.52. The correlation between the total scores of NPAD–DLV and NDI–DLV was 0.77. Twenty six hypotheses were not rejected and one hypothesis was rejected.ConclusionThe NPAD–DLV and NDI–DLV are valid measures of self-reported neck-pain related disability.

PurposeTo investigate relevant change on the Neck Pain and Disability Scale (NPAD) and Neck Disability Index (NDI) and which questionnaire is the most responsive in patients with non-specific chronic neck pain (CNP).MethodsSeventy-six patients with non-specific CNP in an outpatient tertiary rehabilitation setting were dichotomized into “improved” and “stable” based on global perceived effect (GPE) scores. To investigate relevant change minimal detectable change (MDC) and minimal important change (MIC) with the receiver operator characteristic (ROC) cut-off point were assessed. Comparison of responsiveness was performed using areas under the ROC curve (AUC) and correlations between change scores of NPAD and NDI, and GPE.ResultsMDC and MIC on NPAD (scale 0–100) were 31.7 and 11.5 points, respectively. MDC and MIC on NDI (scale 0–50) were 8.4 and 3.5 points, respectively. Changes should exceed this MDC or MIC cut-off to be interpreted as relevant. AUC was 0.75 for both NPAD and NDI. Correlations between change scores of NPAD and NDI, and GPE were, respectively, 0.48 (95 % CI 0.29–0.64) and 0.49 (95 % CI 0.30–0.64).ConclusionsRelevant change on both NPAD and NDI assessed with MDC and MIC resulted in different cut-offs and consequently with different amounts of certainty that the patient is improved. Responsiveness of NPAD and NDI was similar.

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