The Patient Assessment Questionnaire: initial validation of a measure of treatment effectiveness for patients with schizophrenia and schizoaffective disorder

Abstract

Investigation of patients' subjective perspective regarding the effectiveness - as opposed to efficacy - of antipsychotic medication has been hampered by a relative shortage of self-report measures of global clinical outcome. This paper presents data supporting the feasibility, inter-item consistency, and construct validity of the Patient Assessment Questionnaire (PAQ)-a self-report measure of psychiatric symptoms, medication side effects and general wellbeing, ultimately intended to assess effectiveness of interventions for schizophrenia-spectrum patients. The original 53-item instrument was developed by a multidisciplinary team which utilized brainstorming sessions for item generation and content analysis, patient focus groups, and expert panel reviews. This instrument and additional validation measures were administered, via Audio Computer-Assisted Self-Interviewing (ACASI), to 300 stable, medicated outpatients diagnosed with schizophrenia or schizoaffective disorder. Item elimination was based on psychometric properties and Item-Response Theory information functions and characteristic curves. Exploratory factor analysis of the resulting 40-item scale yielded a five factor solution. The five subscales (General Distress, Side Effects, Psychotic Symptoms, Cognitive Symptoms, Sleep) showed robust convergent (β's=0.34-0.75, average β=0.49) and discriminant validity. The PAQ demonstrates feasibility, reliability, and construct validity as a self-report measure of multiple domains pertinent to effectiveness. Future research needs to establish the PAQ's sensitivity to change.