Increasing the sensitivity of the AQoL inventory for the evaluation of interventions affecting mental health

This paper presents the rationale and psychometric analysis for extending the inventory of the Assessment of Quality of Life (AQoL)-6D instrument. The resulting AQoL-8D has an 8 dimensional, 35 item inventory with greater sensitivity in the domain of mental health.The paper briefly reviews the existing QoL instruments used for economic evaluation of health programs. It outlines the steps adopted in developing the AQoL descriptive inventories and, specifically, the methods adopted for data collection and analysis for the AQoL-8D inventory.Three instruments are presented. The first, PsyQoL, is a 22 item instrument which represents the best statistical fit for the measurement of mental health related quality of life. The second, PsyQoL-Brief is a reduced form instrument which is combined with AQoL-6D as the basis for the third instrument, the AQoL-8D. Psychometric properties of the first instrument are excellent and the second are good. The full AQoL-8D has satisfactory properties. Results from a comparison with the original AQoL-6D are reported. The mental health content of AQoL-8D is unique amongst MAU instruments and, along with other AQoL instruments, unique in its derivation from psychometric analysis. Its application to mental health patients and the public demonstrates its ability to discriminate between the groups with greater sensitivity than the previous AQoL-6D instrument.