Validation of the adult attention-deficit/hyperactivity disorder quality-of-life scale in European patients: comparison with patients from the USA

The adult attention-deficit/hyperactivity disorder (ADHD) quality-of-life (AAQoL) scale was previously validated in adult patients in the USA; here, the AAQoL is validated in adult European patients. Data from a 12-week open-label acute treatment period with atomoxetine (80-100 mg/day) in adults with ADHD were used. Patients (>= 18 to <= 50 years old) had a score >= 2 on >= 6 items on the inattentive or hyperactive core subscales of Conners' Adult ADHD Rating Scale-Investigator Rated: Screening Version (CAARS-Inv: SV); a CAARS-Inv: SV 18-item total ADHD symptom score >= 20; and Conners' Adult ADHD Rating Scale-Observer: Screening Version 6-item inattentive or hyperactive core subscale scores >= 2. Data were stratified based on patients' geographic region (Europe vs USA). Scale validation psychometric properties results were very similar between European (n = 1,217; 57.7 % male; mean age 33.0 years) and US (n = 602; 62.1 % male; mean age 33.5 years) patients, including factor loading, internal consistency, convergent and discriminant validity, and responsiveness. Exploratory factor analysis confirmed four AAQoL subscales. Internal consistency was acceptable (Cronbach's alpha > 0.70 for all subscales). The AAQoL total score showed moderate convergent validity with CAARS-Inv: SV 18-item total ADHD symptom and clinical global impression-ADHD-severity (CGI-ADHD-S) scores; and strong convergent validity with Behavior Rating Inventory of Executive Function-Adult Version: Self-Report Global-Executive-Composite Index scores. Mean AAQoL total scores were significantly different among patients grouped by CGI-ADHD-S scores, suggesting good discriminant validity. The AAQoL total and subscale scores presented good responsiveness from baseline to 12 weeks. The AAQoL scale shows comparable validity in European and US adults with ADHD.