Assessing health-related quality of life in people with aphasia
Background: Health related quality of life (HRQL) measures are becoming increasingly used in the evaluation of health care interventions. They allow us to better understand the impact of disease on a patient's life as a whole and to incorporate the patient's perspective in clinical decision making and in the evaluation of health care. A number of studies have explored the HRQL of people with stroke. Still, due to a number of conceptual and methodological issues, there is no clear understanding of the HRQL of a stroke subgroup: people with aphasia. Aims: The broad aim of this research was to explore the HRQL of people with chronic aphasia following stroke in a way that could be replicated in clinical practice. Thus, a single stroke-specific scale (the SS-QOL) was chosen for the assessment of HRQL. The specific research questions that were addressed were: A) Can an acceptable, reliable and valid version of the SS-QOL be developed for people with chronic aphasia? This involved: i) development of an aphasia-adapted version of the SS-QOL and ii) evaluation of its psychometric properties. B) What are the predictors of HRQL in people with chronic aphasia, as measured by the aphasia adapted version of the SS-QOL? Methods: The development of an aphasia-adapted version of the SS-QOL involved consultation with professionals with experience in measure development, language and aphasia, and pilot testing for the modification of the instrument, and a pre-test of the adapted version with 18 people with aphasia. This process resulted in the Stroke and Aphasia Quality of Life Scale (SAQOL). A cross-sectional interview-based survey study was undertaken to evaluate the psychometric properties (acceptability, reliability and validity) of the SAQOL and to determine the predictors of HRQL as measured by the SAQOL. Convenience sampling was used in the pilot and pre-test studies and cluster sampling in the survey study. Measures: HRQL was measured with the SAQOL. In the construct validation of the SAQOL, the following measures were used: for emotional distress the GHQ-12, for cognition the RCPM, for activities the FAI, for social support the SSS and for language the FAST and the ASHA-FACS. Potential predictors of HRQL included demographic, stroke-related variables and variables implicated in previous research or of theoretical interest measured with the following instruments: the GHQ-12, the FAI, the SSS, the ASHA-FACS, the RCPh1 and the PSI (patients' satisfaction with stroke care). Results A) i) Development of an aphasia-adaptedv ersion of the SS-QOL resulted in the SAQOL, an interview administered self-report measure. People with moderate or mild receptive aphasia (as determined by a score of >_ 7 in the receptive domains of the FAST) found the SAQOL acceptable and were able to self-report to it. A) ii) Psychometric evaluation: 83 out of 95 participants self-reported on the SAQOL. The results supported the reliability and the validity of the overall SAQOL, but not of its subdomains' structure. A shorter 39-item version was derived through factor analysis (SAQOL-39). This instrument had a stable, conceptually clear 4-factor structure (physical, psychosocial, communication and energy) and high acceptability, internal consistency [scale(a= .93) and subdomains' (a=. 74-. 94)], test-retest reliability [scale (ICC=. 98) and subdomains' (ICC=. 89-. 98)] and construct validity [corrected domain-total correlations (r=. 38-. 58), subdomains' convergent (r=. 55-. 67) and discriminant (r=. 02-. 27), and scale's discriminant (r=. 19-. 31) and correlated measures (r=. 45-. 58)]. B) Predictors of HRQL: High emotional distress, reduced involvement in home and outdoors activities, high communication disability and >_2 comorbid conditions predicted poorer HRQL (adjusted R2=. 52). Stroke type (infarct vs haemorrhage) and demographic variables (age, gender, ethnicity, marital status, employment status and socioeconomic status) were not significant predictors of HRQL in these participants. Conclusions:The SAQOL-39 is an acceptable, reliable and valid measure for the assessment of HRQL in people with chronic aphasia. Further testing is needed to establish the usability of this measure in evaluative research and routine clinical practice. Poor HRQL is predicted by distress, reduced involvement in activities, communication disability and comorbidity. Service providers need to take these factors into account when designing intervention programmes.