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52. Testing a bifactor model of the quality of life scale in first episode psychosis
The Heinrich’s Quality of Life Scale (QLS) is a semi-structured interview commonly used to assess functional outcomes in schizophrenia. The QLS was originally designed to assess four sub domains, including Interpersonal relations, Instrumental role, Intrapsychic foundations, and Common objects and activities. A recent analysis, however, identified three factors, including Interpersonal functioning, Instrumental functioning, and Motivation as having the best fit. In psychosis intervention research, the QLS total score is typically used as a primary outcome measure. It is unclear if the QLS total score has support as a unidimensional construct of overall function. Thus, the primary aim of the current study was to test a bifactor model of the QLS in first episode psychosis to test the fit of a general factor in addition to specific factors. Participants (N = 403) were enrolled in the Recovery After an Initial Schizophrenia Episode - Early Treatment Program (RAISE-ETP). Fit for a 3-factor confirmatory solution was compared to that of a confirmatory bifactor solution. The best fitting model consisted of a general factor and 3 specific factors (Interpersonal relations, Instrumental functioning, and Motivation). Items representing Interpersonal relations and Instrumental functioning loaded highly on both the general factor and their respective specific factors. In contrast, items tapping motivation loaded highly on the general factor but not the specific factor, suggesting unidimensionality with the total score. Findings reveal that the QLS total score appears to assess levels of motivation, but may not be appropriate for assessing specific outcomes relating to interpersonal relations and instrumental functioning. Model invariance testing between groups (schizophrenia, schizoaffective disorder), gender, and occupation will also be presented and discussed.