Measuring clinical outcomes in adult ADHD clinics: psychometrics of a new scale, the adult ADHD Clinical Outcome Scale

Background Adult attention-deficit hyperactivity disorder (ADHD) clinics are in their infancy in Ireland and internationally. There is an urgent need for clinical evaluation of these services. Until now, clinical outcomes have relied mainly on functional scales and/or quality of life. However, adult ADHD is a longstanding disorder with many comorbidities. Although medication for ADHD symptoms can have immediate effects, co-occurring problems may take considerably longer to remediate. Aims To present the psychometrics of a short outcome measure of key clinical areas including symptoms. Method The ADHD Clinical Outcome Scale (ACOS), developed by the authors, is a clinician-rated scale and was administered in consecutive adults attending an ADHD clinic. A modified version was completed by the participant. A second clinician independently administered the scale in a subsample. ACOS consists of 15 items rated on a Likert scale. Two self-report scales, the Adult ADHD Quality of Life Questionnaire (AAQoL) and Weiss Functional Impairment Rating Scale (WFIRS), were also administered. Results The mean age of 148 participants was 30.1 years (s.d. = 9.71), and 81 were female (54.7%). The correlation for interrater reliability was r = 0.868, and that between the participant and clinician versions was r = 0.663. The intraclass correlation coefficient for the internal consistency was 0.829, and the correlations for concurrent validity with total AAQoL and WFIRS scores were r = −0.573 and r = 0.477, respectively. Factor analysis revealed four factors: (a) attentional/organisational problems; (b) hyperactivity/impulsivity; (c) comorbidities; and (d) alcohol/drug use, self-harm and tension in relationships. Conclusions The psychometrics of the ACOS are promising, and the inclusion of typically co-occurring clinical domains makes it suitable for use as a clinician-rated outcome measure in every contact with patients attending adult ADHD clinics