Abstract
Background
Understanding caregiver strain may be crucial to determine which interventions are most needed to mitigate the negative impact of caring for people with multiple sclerosis (MS). The Caregiver Strain Index (CSI) is a brief self-assessment tool for measuring the caregivers’ perceived level of burden. Limited information is available on the psychometric performance of the CSI in MS.
Objective
The objective of this study was to assess the factor structure and construct validity of the CSI in MS.
Methods
A multicenter, cross-sectional study in adults with relapsing-remitting and primary-progressive MS (McDonald 2010 criteria) was conducted. A non-parametric item response theory (IRT) procedure, Mokken analysis, was conducted to assess the dimensional structure of the CSI. A parametric IRT model for dichotomous responses, Rasch model, was conducted to assess item characteristics. Discriminative validity was assessed comparing the distribution of its overall score between people with mild and moderate-severe disability according to the Expanded Disability Status Scale.
Results
A total of 72 MS caregivers were studied. The prevalence of a high level of strain was 23.6% (n=17). Internal reliability was high (Cronbach’s alpha =0.91). According to Mokken analysis, CSI represented a unidimensional construct of caregiver burden although two of the total 13 items (#1 and #13) could not be assigned to any factor by an automatic item selection procedure. Without these items, the scalability moved from a weak (Hi =0.37) to a medium scale (Hi =0.44). However, the item characteristic curve of the Rasch model showed a range of appropriate difficulty and the item and person parameters showed good fit (Andersen likelihood ratio test =18.40, df =11; P-value =0.07; all item values for the infit). The CSI score showed a good discriminative validity between the levels of disability of the care recipient.
Conclusion
The CSI questionnaire shows appropriate psychometric characteristics being a useful instrument to assess different aspects of burden in MS caregivers in clinical practice.
Acknowledgments
The W-IMPACT Clinical Investigators: Adrián Ares (Complejo Asistencial Universitario de León), Carmen Arnal (Complejo Hospitalario Universitario de Granada), Ana B Caminero (Hospital Nuestra Señora de Sonsoles, Ávila), María Carcelén (Hospital General Universitario de Valencia), Olga Carmona (Hospital de Figueres), Pablo Eguía (Hospital Dr José Molina Orosa, Lanzarote), María del Carmen Fernández (Hospital Universitario Virgen de Valme, Sevilla), Ricardo Ginestal (Hospital Clinico San Carlos, Madrid), Laura Lacruz (Hospital Francesc de Borja, Gandía), Miguel Llaneza (Hospital Arquitecto Marcide, Ferrol), Carlos López de Silanes (Hospital de Torrejón, Torrejón de Ardoz), Gisela Martín (Hospital Verge de la Cinta, Tortosa), Laura Navarro (Hospital General Universitario de Elche), Beatriz Romero (Hospital Son Llatzer, Palma de Mallorca), María Seral (Hospital General San Jorge, Huesca), Myriam Solar (Hospital Universitario de Cabueñes, Gijón). The abstract of this paper was presented at the 4th Congress of the European Academy of Neurology as a poster presentation with interim findings. The poster’s abstract was published in “ePoster Sessions” in European Journal of Neurology (https://doi.org/10.1111/ene.13699). The study was funded by Roche Farma, Spain.
Disclosure
DP and JM are employees of Roche Farma Spain. The other authors report no conflicts of interest in this work.