Rasch analysis of the carers quality of life questionnaire for parkinsonism.

OBJECTIVE

To assess the psychometric properties of the Carers Quality of Life Questionnaire for Parkinsonism using a Rasch modeling approach and determine the optimal cut-off score.

METHODS

We performed a Rasch analysis of the survey answers of 430 carers of patients with atypical parkinsonism.

RESULTS

All of the scale items demonstrated acceptable goodness of fit to the Rasch model. The scale was unidimensional and no notable differential item functioning was detected in the items regarding age and disease type. Rating categories were functioning adequately in all scale items. The scale had high reliability (.95) and construct validity and a high degree of precision, distinguishing between 5 distinct groups of carers with different levels of quality of life. A cut-off score of 62 was found to have the optimal screening accuracy based on Hospital Anxiety and Depression Scale subscores.

CONCLUSION

The results suggest that the Carers Quality of Life Questionnaire for Parkinsonism is a useful scale to assess carers' quality of life and allows analyses requiring interval scaling of variables. © 2016 International Parkinson and Movement Disorder Society.