Validation of the questionnaire for impulsive-compulsive disorders in Parkinson's disease (QUIP) and the QUIP-rating scale in a German speaking sample.

Impulsive-compulsive disorders are frequent in patients with Parkinson's disease (PD). Recently, a screening questionnaire and rating scale were developed for these disorders: the questionnaire for impulsive-compulsive disorders (QUIP) and QUIP-rating scale (QUIP-RS). We assessed the validity of these instruments in the German language in order to reevaluate the benefit and to obtain German screening tools in clinical practice. A convenience sample of 156 patients was assessed in Kiel and Vienna. The patients filled out the QUIP-current, the QUIP-anytime and the QUIP-RS. We validated the questionnaires against a gold standard diagnosis via receiver operating characteristic curves and determined optimal cut-off scores for the instruments. Excluding walkabout, which was not shown to be valid, sensitivities ranged from 60-92 % for the QUIP-current, 68-91 % for the QUIP-anytime, and 73-100 % for the QUIP-RS. Specificities were >71 % for QUIP-current, >69 % for QUIP-anytime and >62 % for QUIP-RS. With its very good sensitivities, the QUIP-RS is a valid instrument to assess impulsive-compulsive disorders and makes an early detection of behavioral disorders in PD possible. The QUIP-anytime was also shown to be a valid screening instrument. Both are expected to prove useful in scientific and clinical practice.