Création et validation d'un autoquestionnaire mesurant la qualité de vie de patients souffrant de schizophrénie : l'échelle schizophrenia quality of life (SOL)

Rationale/Objective - Quality of Life (QOL) has been recognized as an important measure of the outcome of patients by clinicians and policy makers in Mental Health. The emerging consensus in the health field that personal values and the patient's preferences are important in monitoring the quality of medical care outcomes makes it even more important to assess the patient's perspectives. Unfortunately, there is little consensus about what constitutes QOL or how to measure it, particularly in psychotic patients. The objective of this study is to report the stages of development and validation of a QOL questionnaire based on issues pertinent to patients with schizophrenia. Method - During a first phase, identical pattern were identified among interviews (conducted by psychologists) of schizophrenic patients (DSM IV, n = 100), mental health staff (n = 20) and families (n = 20). The data gathered in the first phase were discussed and organized, by 25 experts, into a structure that made up the skeleton of the scale (133 items, 17 factors). Based on a prospective epidemiological study conducted with 337 French psychiatrists, a validation analysis of structural and psychometric proprieties was performed. Finally reliability of the scale was assessed by a second test/retest (D0, D7) study (n = 100). Results - A total of 686 schizophrenic, schizophreniform or schizoaffective patients (DSM IV) were included. Internal consistency analysis identified 14 factors (74 items), all with a Cronbach's alpha of at least 0.75 : professional life (0.95), affective and sexual life (0.92), illness knowledge (0.90), relationship (0.92), life satisfaction, (0.87), coping with drugs (0.79), drugs impact on the body (0.87), daily life (0.83), family relationship (0.81), future (0.88), security feeling (0.84), leisure (0.87), money management (0.76) and autonomy (0.75). Construct validity was confirmed (Pearson test) using established clinical (Brief Psychiatry Rating Scale and Clinical Global Improvement), social (Psychological Aptitude Rating Scale) and generic quality of life (Functional Status questionnaire) measures, correlation coefficient was significant for all factors but 2 in the BPRS (illness knowledge and coping with drugs) and 3 in the CGI (illness knowledge, coping with drugs and life satisfaction). Lastly, test/retest indicated high reliability for each factor (p < 0.001), the lower correlation coefficient (r) was 0.526. Conclusions-The Schizophrenia Quality Of Life-scale (SOL), based on a patient's point of view approach, is an efficient, multidimensional instrument designed for the measurement of the consequences of schizophrenia on individuals' lives.