Psychometric Properties of the German Version of the Whiplash Disability Questionnaire

Objective: For the management of whiplash-associated disorders the use of patient oriented disability questionnaires are of uppermost importance. The Australian whiplash disability questionnaire has a high content, face and constructs validity, and an excellent short- and medium-term reproducibility. However, until now no German version of this questionnaire is available. Aim: A cross-cultural adaptation of the whiplash disability questionnaire for a German-speaking population with ensured retention of psychometric properties such as validity and reliability of the translated version. Settings: Acute and chronic settings. Subject: A total of 75 patients (67 acute/8 chronic) and a control group of 177 asymptomatic volunteers were analyzed. Interventions: All participants completed the translated 13-item questionnaire as well as documented their current health state on a visual analog scale (VAShealth) and a general disability questionnaire (EQ-5D) for comparison. For test-retest reliability assessment 16 chronic patients and 25 healthy persons completed the questionnaire twice with an interval of 2 weeks. Main measures: Construct and concurrent validity and test-retest reliability. Results : The translated version showed no floor or ceiling effects, a high internal consistency (Cronbach’s alpha=0.95) and a very good inter-item correlation (rho=0.926). The concurrent validity testing using EQ-5D score as the reference showed a significant correlation to the whiplash disability questionnaire (overall rho=0.838, acute patients rho=0.749, chronic patients rho=0.876; p<0.001 each) and to the VAShealth (overall rho=-0.74, acute patients rho=-0.66, chronic patients rho=-0.65; p<0.001 each). The intra-class coefficient (0.969) indicated high short term reproducibility. Discussion : The German version of the whiplash disability questionnaire is valid and reliable as outcome measure for acute and chronic study settings.