Validation of the questionnaire for impulsive-compulsive disorders in Parkinson's disease

As no comprehensive assessment instrument for impulse control disorders (ICDs) in Parkinson's disease (PD) exists, the aim of this study was to design and assess the psychometric properties of a self-administered screening questionnaire for ICDs and other compulsive behaviors in PD. The Questionnaire for Impulsive-Compulsive Disorders in Parkinson's Disease (QUIP) has 3 sections: Section 1 assesses four ICDs (involving gambling, sexual, buying, and eating behaviors), Section 2 other compulsive behaviors (punding, hobbyism, and walkabout), and Section 3 compulsive medication use. For validation, a convenience sample of 157 PD patients at 4 movement disorders centers first completed the QUIP, and then was administered a diagnostic interview by a trained rater blinded to the QUIP results. A shortened instrument (QUIP-S) was then explored. The discriminant validity of the QUIP was high for each disorder or behavior (receiver operating characteristic area under the curve [ROC AUC]: gambling = 0.95, sexual behavior = 0.97, buying = 0.87, eating = 0.88, punding = 0.78, hobbyism = 0.93, walkabout = 0.79). On post hoc analysis, the QUIP-S ICD section had similar properties (ROC AUC: gambling = 0.95, sexual behavior = 0.96, buying = 0.87, eating = 0.88). When disorders/behaviors were combined, the sensitivity of the QUIP and QUIP-S to detect an individual with any disorder was 96 and 94%, respectively. Scores on the QUIP appear to be valid as a self-assessment screening instrument for a range of ICDs and other compulsive behaviors that occur in PD, and a shortened version may perform as well as the full version. A positive screen should be followed by a comprehensive, clinical interview to determine the range and severity of symptoms, as well as need for clinical management.