Proxy and self-report agreement on the Stroke and Aphasia Quality of Life Scale-39
- 1 Department of Language and Communication Science, Institute of Health Sciences, City University, London, UK
- 2 Department of Speech and Language Therapy, Bromley Primary Care Trust, Kent, UK
- 3 Department of Practice and Policy, School of Pharmacy, University of London, London, UK
- Dr Katerina Hilari, Department of Language and Communication Science, City University, Northampton Square, London EC1V 0HB, UK;
- Received 18 November 2006
- Revised 11 January 2007
- Accepted 11 January 2007
- Published Online First 26 January 2007
Background and purpose: Health related quality of life outcomes are increasingly used to measure the effectiveness of stroke interventions. People with severe aphasia after stroke may be unable to self-report on such measures, necessitating the use of proxy respondents. We explored the level of agreement between people with aphasia (PWA) and their proxies on the Stroke and Aphasia Quality of Life Scale (SAQOL-39) and whether this agreement is influenced by demographic variables and proxy levels of depression and carer strain.
Methods: People with chronic aphasia (⩾6 months post stroke) were recruited through the UK national charity for PWA. They were interviewed on the SAQOL-39 and their nominated proxies were interviewed on the SAQOL-39, the General Health Questionnaire and the Caregiver Strain Index. Proxy respondents had to be ⩾18 years of age, see the person with aphasia at least twice a week and have no known severe mental health problems or cognitive decline.
Results: 50 of 55 eligible pairs (91%) took part in the study. Proxies rated PWA as more severely affected than PWA rated themselves. The SDs of the difference scores were large and the difference was significant for three of the four SAQOL-39 domains and the overall mean (p⩽0.01). However, the bias as indicated by effect sizes was small to moderate (0.2–0.5). The strength of the agreement was excellent for the overall SAQOL-39 and the physical domain (intra-class correlation coefficient ICC 0.8), good for the psychosocial and communication domains (0.7) and fair for the energy domain (0.5). Demographic variables and proxy’s mood and carer strain did not affect the level of agreement.
Conclusions: For group comparisons, proxy respondents who are in frequent contact with people with chronic aphasia can reliably report on their health related quality of life, using the SAQOL-39. Although there are significant differences between PWA and proxy responses, the magnitude of this difference is small to moderate.
Competing interests: None.
- Caregiver Strain Index
- Frenchay Aphasia Screening Test
- General Health Questionnaire
- health related quality of life
- intra-class correlation coefficient
- people with aphasia
- Stroke and Aphasia Quality of Life Scale-39
- Sickness Impact Profile
- Stroke Impact Scale
- Stroke Specific Quality of Life Scale