A psychometric comparison of two Carer Quality of Life Questionnaires in Huntington's disease: implications for neurodegenerative disorders

Background: The carer impact of neurodegenerative disorders such as Huntington's disease (HD) is vast. Attempts to measure carer QoL in neurodegenerative disorders include the three-dimensional (Practical aspects of Caregiving, PC; Satisfaction with Life, SL; Feelings about Living with Huntington's disease, FL) Huntington's Disease Quality of Life Battery for Carers (HDQoL-C) and the unidimensional Alzheimer's Carer's Quality of Life Inventory (ACQLI). However, evidence regarding their psychometric properties is sparse. Objectives: To test and compare the psychometric properties of the HDQoL-C, its short-form, and the ACQLI among HD carers. Methods: Data from 61 HD carers (36 women; mean age, 55) were analysed using traditional psychometric methods. Results: Data completeness was good (>95% computable scale scores) but compromised for the PC and total HDQoL-C scales (≤80% computable scale scores). Scaling assumptions were supported for the SL and ACQLI scales (corrected item-total correlations ≥0.38; scaling success rates, 94–100%) but not for the PC, FL or total HDQoL-C scales (corrected item-total correlations ≥0.08; scaling success rates, 39–62%). Floor/ceiling effects were ≤9.8%. Reliabilities were ≥0.84, except for the PC scale (0.62). Conclusions: The HDQoL-C failed to exhibit suitability as a HD carer outcome measure, as two of its three scales did not meet basic psychometric criteria. The third scale (SL) did not outperform the ACQLI. This suggests that carer impact is not disease specific across neurodegenerative disorders.