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(Stroke. 2003;34:1944.)
© 2003 American Heart Association, Inc.

Original Contributions

Stroke and Aphasia Quality of Life Scale-39 (SAQOL-39)

Evaluation of Acceptability, Reliability, and Validity

Katerina Hilari, PhD; Sally Byng, PhD; Donna L. Lamping, PhD Sarah C. Smith, PhD

From the Department of Language and Communication Science, Institute of Health, City University, London, UK.

Reprint requests Dr Katerina Hilari, Department of Language and Communication Science, City University, Northampton Square, London EC1V 0HB, UK. E-mail k.hilari{at}city.ac.uk

	Abstract

Top Abstract Introduction Subjects and Methods Results Discussion References

 
Background and Purpose— Health-related quality of life (HRQL) is a key outcome in stroke clinical trials. Stroke-specific HRQL scales (eg, SS-QOL, SIS) have generally been developed with samples of stroke survivors that exclude people with aphasia. We adapted the SS-QOL for use with people with aphasia to produce the Stroke and Aphasia Quality of Life Scale (SAQOL). We report results from the psychometric evaluation of the initial 53-item SAQOL and the item-reduced SAQOL-39.

Methods— We studied 95 people with long-term aphasia to evaluate the acceptability, reliability, and validity of the SAQOL and SAQOL-39 using standard psychometric methods.

Results— A total of 83 of 95 (87%) were able to complete the SAQOL by self-report; their results are reported here. Results supported the reliability and validity of the overall score on the 53-item SAQOL, but there was little support for hypothesized subdomains. Using factor analysis, we derived a shorter version (SAQOL-39) that identified 4 subdomains (physical, psychosocial, communication, and energy). The SAQOL-39 demonstrated good acceptability, internal consistency (Cronbach’s =0.74 to 0.94), test-retest reliability (intraclass correlation coefficient=0.89 to 0.98), and construct validity (corrected domain–total correlations, r=0.38 to 0.58; convergent, r=0.55 to 0.67; discriminant, r=0.02 to 0.27 validity).

Conclusions— The SAQOL-39 is an acceptable, reliable, and valid measure of HRQL in people with long-term aphasia. Further testing is needed to evaluate the responsiveness of the SAQOL-39 and to investigate its usefulness in evaluative research and routine clinical practice.

Key Words: aphasia • outcome • quality of life • stroke

	Introduction

Top Abstract Introduction Subjects and Methods Results Discussion References

 
Outcome measures that incorporate patients’ views about health-related quality of life (HRQL) are now commonly used to evaluate healthcare interventions. HRQL refers to the impact of health on a person’s ability to lead a fulfilling life¹ and generally incorporates the individual’s perceptions of physical, mental/emotional, family, and social functioning.^2–4 Measures of HRQL are particularly relevant in stroke when the key aims of rehabilitation are to facilitate adaptation to disability, to promote social and community integration, and to maximize well-being and quality of life.⁵ Although a number of stroke-specific quality-of-life scales have been developed,^6–9 most exclude stroke survivors with aphasia and/or cognitive decline who are in fact those most prone to social isolation and exclusion.^10,11 A stroke-specific HRQL scale that is appropriate for use with people with aphasia is needed for clinical trials and service evaluation.

We adapted the Stroke-Specific Quality of Life Scale (SS-QOL)⁹ for use with people with aphasia, producing the Stroke and Aphasia Quality of Life Scale (SAQOL). Here, we report results from the psychometric evaluation of the initial 53-item SAQOL and the item-reduced SAQOL-39.

	Subjects and Methods

Top Abstract Introduction Subjects and Methods Results Discussion References

 
The SAQOL
The development of the SAQOL has been previously reported.^12,13 In short, the SAQOL is an interview-administered self-report scale that comprises the 49 items of the SS-QOL (modified to be communicatively accessible to people with aphasia) and 4 additional items to increase its content validity with this population. These 4 items focus on difficulties with understanding speech, difficulties with making decisions, and the impact of language problems on family life and social life. Changes to the SS-QOL to produce the SAQOL were made through consultation with expert professionals and pilot testing with people with aphasia. The SAQOL was then pretested with 18 people with aphasia with good results.^12,13

The 53 items of the SAQOL were hypothesized to group into 12 subdomains based on the SS-QOL: self-care, mobility, upper-extremity function, work, vision, language, thinking, personality, mood, energy, and family and social roles. The SAQOL has 2 response formats, both based on a 5-point scale: 1=could not do it at all to 5=no trouble at all and 1=definitely yes to 5=definitely no. Overall and subdomain scores can range from 1 to 5; the overall SAQOL score is calculated by summing across the items and dividing by the number of items; subdomain scores are calculated the same way.

Design and Participants
The study design was a cross-sectional, interview-based psychometric study. Participants were recruited from 3 settings: 2 speech and language therapy (SLT) service providers, 1 inner city and 1 semirural, and 1 not-for-profit organization for people with aphasia. The target population was people with long-term aphasia. Inclusion criteria were as follows: aphasia resulting from stroke of at least 1-year duration, no known prestroke history of severe cognitive decline or mental health problems, and living at home before the stroke. Participants were identified through review of the SLT records at each site. Eligible participants were invited to take part in the study, and written consent was obtained from those willing to take part. Test-retest reliability data were collected within a period of 2 to 14 days from the participants at the first recruitment site who agreed to have the SAQOL administered twice.

Procedure and Measures
Participants were interviewed at home or at the SLT site. We used the Frenchay Aphasia Screening Test (FAST)¹⁴ to screen for aphasia. The total FAST score determined overall aphasia severity and the receptive FAST score determined which participants were able to self-report. A FAST receptive score of 7 of 15 was used as a cutoff score below which significant others provided proxy reports. Measures included the SAQOL, General Health Questionnaire (GHQ-12),¹⁵ Raven’s Colored Progressive Matrices (RCPM),¹⁶ Frenchay Activities Index (FAI),¹⁷ and MOS Social Support Survey (SSS).¹⁸ Participants were also asked to rate their overall quality of life compared with before the stroke on a 5-point scale (1=a lot worse, 5=better than before the stroke). The American Speech and Hearing Association Functional Assessment of Communication Skills for Adults (ASHA-FACS)¹⁹ was also completed for each participant.

Psychometric Analyses
We used gold standard methods^20,21 to evaluate the psychometric properties of the SAQOL using a strategy developed in previous work.²² Table 1 summarizes the psychometric tests and criteria used to evaluate acceptability, reliability, and validity.^23–25 Data analyses were carried out with SPSS 10.0 for Windows.²³

View this table: [in this window] [in a new window]   TABLE 1. Psychometric Tests and Criteria

View this table: [in this window] [in a new window]   TABLE 4. Convergent and Discriminant Validity of SAQOL and SAQOL-39

	Results

Top Abstract Introduction Subjects and Methods Results Discussion References

 
Respondents
A total of 95 of 116 eligible participants (82%) agreed to take part. Of these, 12 were excluded from analyses because they were unable to self-report on the questionnaires (<7 of 15 on the receptive domains of the FAST), leaving 83 subjects. Most of the sample was male (62.7%), white (78.3%), and married or had a partner (62.6%), and 43.4% were >65 years of age (Table 2).²⁶

View this table: [in this window] [in a new window]   TABLE 2. Respondent Characteristics

Stage 1: Psychometric Evaluation of the 53-Item SAQOL
Acceptability and Reliability
The SAQOL had minimal missing data and floor/ceiling effects, but 11 items (21%) showed unacceptable skew (Table 3). The overall scale had good internal consistency (=0.93). Four of the hypothesized subdomains failed the criterion for internal consistency 0.70 (work, vision, personality, and family roles). Test-retest reliability data were collected from 17 participants. Their characteristics were similar to those of the overall sample in terms of age, sex, marital status, and overall and receptive FAST scores. The SAQOL showed excellent test-retest reliability for the overall score (intraclass correlation coefficient [ICC]=0.98) and for the 12 subdomains (ICC=0.84 to 0.99).

View this table: [in this window] [in a new window]   TABLE 3. Acceptability and Reliability of SAQOL and SAQOL-39

Validity
Within-Scale Analyses
All hypothesized subscales were moderately to highly correlated (r=0.39 to 0.73) with the total score, except for vision (r=0.26). As expected, subscales measuring related constructs (eg, self-care, mobility, work) were correlated (r=0.73 to 0.78), whereas correlations were lower between less related subscales (eg, self-care and mood; r=0.29). All intercorrelations between subscales were below the criterion of 0.80, except for self-care with upper extremities (r=0.84).

The results of principal components analysis (PCA) indicated that 5 items did not load highly (<0.20) on the general component. Principal axis factor analysis (PAF) with varimax rotation was used to evaluate the 12 hypothesized subdomains. The results did not support the 12-subdomain structure of the SAQOL, and no clear alternative models were identified.

Comparisons With External Criteria
Analysis of variance of mean SAQOL scores showed significant differences between respondents who were better/same, worse, or a lot worse than before the stroke (F^{(2, 80)}=11.340; P<0.001; pairwise comparisons, P<0.05), thus supporting the construct validity of the SAQOL. Comparisons with external measures (Table 4) provide further support for convergent (r=0.44 to 0.59) and discriminant (r=0.26 to 0.29) validity of the overall SAQOL. Results, however, do not support the construct validity of 4 of the tested subscales (thinking, mood, family roles, and social roles).

Stage 2: Development and Psychometric Evaluation of the SAQOL-39
Principal axis factor analysis with varimax rotation was used to develop an item-reduced version of the SAQOL and to identify a conceptually clear and psychometrically sound subdomain structure. Results of the KMO test showed adequate sampling adequacy, and Bartlett’s test of sphericity was significant for all models. Preliminary analyses produced a 7-factor model. A total of 14 items that did not load (<0.40) or that cross-loaded were removed, and the analyses were repeated on the remaining 39 items. The final model for the reduced 39-item SAQOL explained 48% of the variance and included 4 factors: physical, psychosocial, communication, and energy (Table 5).

View this table: [in this window] [in a new window]   TABLE 5. Factor Structure of the SAQOL-39

Acceptability and Reliability
The acceptability of the SAQOL-39 is demonstrated by minimal missing data and floor/ceiling effects and only 4 skewed items (Table 3). It shows good internal consistency and test-retest reliability for scale (=0.93; ICC=0.98) and subscale scores (=0.74 to 0.94; ICC=0.89 to 0.98).

Validity
Within-Scale Analyses
Intercorrelations between SAQOL-39 subscale scores (r=0.10 to 0.47) and correlations between subscale and total scores (r=0.38 to 0.58) are all acceptable. Results support the 4-factor model described above.

Comparisons With External Criteria
Results (Table 4) provide good support for known groups (F^{(2, 80)}=10.609, P<0.001; pairwise comparisons, P<0.05), convergent (r=0.46 to 0.58), and discriminant (r=0.19 to 0.27) validity. The physical, communication, and energy subscales show good convergent (r=0.39 to 0.67, r=0.55, r=0.32, respectively) and discriminant (r=0.10 to 0.26, r=0.08 to 0.21, r=-0.10 to 0.14, respectively) validity. The psychosocial subdomain shows good discriminant (r=0.12 to 0.20) and adequate convergent (r=0.28 to 0.62) validity with only 1 correlation lower than predicted (r=0.28 with the SSS).

	Discussion

Top Abstract Introduction Subjects and Methods Results Discussion References

 
Existing quality-of-life scales are hard to use with people with aphasia who may have difficulty understanding some of the items or expressing their responses. We modified a stroke-specific scale, the SS-QOL, for use with people with aphasia and tested its psychometric properties in a group of people with long-term aphasia. The fact that 87% of the respondents (83 of 95) were able to self-report in an interview format suggests that use of the SAQOL would allow most stroke survivors to be included in trials, thus minimizing the need for proxy respondents. This is important because there tends to be a significant difference in proxy and self-reports of functional status and quality of life after stroke.^27,28

Although our results confirm the acceptability, reliability, and validity of the 53-item SAQOL, there is little support for its hypothesized subdomain structure. We therefore used factor analysis to develop a shorter 39-item version. The SAQOL-39 shows good acceptability, internal consistency, test-retest reliability, and construct validity. Moreover, there is support for 4 conceptually clear and psychometrically robust subdomains (physical, psychosocial, communication, and energy), which have been consistently identified by stroke survivors as among the areas of functioning most affected by stroke.^6,9,11 The SAQOL-39 is therefore a highly relevant measure for stroke survivors that is relatively short and does not produce significant respondent burden.

An important consideration is the representativeness of our sample. Although there are no comparison data for stroke survivors with aphasia, respondents in this study are similar to stroke survivors in the United Kingdom. Stroke is more common in men and in older people²⁹; in our sample, 63% were male and 44% were >65 years old. In the study area, 24% of the population is black or Asian³⁰ compared with 22% in our sample. There were, however, differences in social class between our sample and the UK stroke population. Stroke is more prevalent in people from manual social classes,²⁹ whereas 57% of our sample was from non-manual social classes. This may reflect the geographical area from which the sample was drawn. Because it is possible that socioeconomic status has an effect on HRQL, we compared the SAQOL-39 scores of our different socioeconomic groups. We found no significant differences in the HRQL of the groups (F^{(7, 75)}=0.64, P0.72), even when we collapsed them in broader social classes (F^{(3, 79)}=0.92, P0.43).

In this study, we used the same sample for item reduction and psychometric evaluation of the SAQOL-39. It is important that the psychometric properties of the SAQOL-39 be re-evaluated in an independent sample. Further psychometric testing should also evaluate the responsiveness of the SAQOL-39.

The SAQOL-39 is a psychometrically robust measure that can be used to assess HRQL in most stroke survivors, including people with aphasia, in clinical practice, and in research. As is common with new measures, further research is needed to confirm its psychometric properties and to determine its appropriateness as a clinical outcome measure. The SAQOL-39 is a new and promising measure for use in treatment and service evaluation, clinical audit, and treatment prioritization.

Copies of the SAQOL-39 and the user’s manual are available from the authors at the reprint request address.

	Acknowledgments

 
This study was funded by the Stroke Association and the Dunhill Medical Trust, London, UK.

Received February 3, 2003; revision received April 10, 2003; accepted April 15, 2003.

	References

Top Abstract Introduction Subjects and Methods Results Discussion References

 

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This Article Abstract Full Text (PDF) All Versions of this Article: 34/8/1944    most recent 01.STR.0000081987.46660.EDv1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Permissions Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Hilari, K. Articles by Smith, S. C. Search for Related Content PubMed PubMed Citation Articles by Hilari, K. Articles by Smith, S. C. Related Collections Health policy and outcome research Other Stroke Treatment - Medical Behavioral/psychosocial - stroke