[A preliminary validation of a new French instrument to assess quality of life for caregivers of patients suffering from schizophrenia].Encephale. 2011 Dec; 37(6):425-32.E
Since psychiatric institutions began discharging mentally ill patients into the community, family of patients suffering from schizophrenia are more and more involved in the therapeutic process. The adverse consequences of having a patient suffering from schizophrenia at home are called "burden of care" and have been studied by numerous authors. We were interested in the quality of life of caregivers and its evaluation. This concept represents a more complex, multidimensional approach in which many variables are taken into account. We propose the development of a French self-administered instrument of quality of life for caregivers of individuals with schizophrenia, the caregiver schizophrenia quality of life questionnaire (S-CGQoL).
Data were collected through the departments of six psychiatric hospitals in France (n=246). The item reduction and validation processes were based on both item response theory and classical test theory. The study of external validity used the generic Short Form 36 questionnaire. Scores of isolated dimensions were also confronted with caregivers' and patients' demographic data and with patients' clinical data.
The S-CGQoL contains 25 items describing seven dimensions (psychological and physical well-being; burden and daily routine; relationships with spouse; relationships with psychiatric team; relationships with family; relationships with friends; and material burden). The seven-factor structure accounted for 74.4% of the total variance. Internal consistency was satisfactory; Cronbach's alpha coefficients ranged from 0.79 to 0.92 in the whole sample. The scalability was satisfactory, with INFIT statistics within an acceptable range. In addition, the results confirmed the absence of DIF and supported the invariance of the item calibrations. Acceptability was good. The study of external validity found significant correlation between S-CGQoL index and all SF-36 dimension scores. Certain dimensions of the S-CGQoL are associated with caregivers' characteristics (age, sex, number of children, living situation, and employment status). Moreover, some domains of caregiver's quality of life are dependant on subtype of schizophrenia (paranoid) and symptomatology (positive factor and general psychopathology). We did not find any correlation with negative factor.
The content of the S-CGQoL encompasses experiences of great importance to patients and is substantially different from other generic quality of life or burden instruments. In our questionnaire, the focus on the different aspect of the social life permits a precise analytical description of the social dimension that is not assessed as much in other questionnaires.
The psychometric properties need to be studied in a wider population. Some parameters of internal validity are missing, such as reproductibility (test-retest reliability) and sensibility to change. The external validity needs to study relationships between S-CGQoL and burden.
The S-CGQoL is the first self-administered quality of life questionnaire for caregivers of patients suffering from schizophrenia. It presents satisfactory psychometric properties, which can be completed in five minutes and, therefore, fulfils the goal of brevity sought in research and clinical practice.