Reference values for and interpretation of the Singapore Caregiver Quality of Life Scale: a quantile regression approach.

PURPOSE: The Singapore Caregiver Quality of Life Scale (SCQOLS) was recently developed and validated in two languages - English and Chinese. The total and domain scores are scaled to range from 0 to 100. However, the scale is not at the interval-ratio level of measurement. To facilitate interpretation, we established the percentiles of the scale's total and domain scores among family caregivers of patients with advanced cancers and demonstrate the effect size in terms of differences in relation to caregiver and patient characteristics. METHODS: Data were drawn from a cross-sectional survey of family caregivers of patients with stage III or IV solid cancers in Singapore. Quantile regression was used to estimate the percentiles in relation to caregiver and patient characteristics. RESULTS: Participants in adjacent categories of patient's performance status and caregiver's having other family members to share caregiving duties differed by 3 to 5 points in median quality of life total score and most domain scores (each Bonferroni-adjusted P, P[B], < 0.05). Ethnicity was associated with the Physical Well-being and Experience & Meaning domain scores (each P[B] < 0.05), with variable direction and magnitude. Education was associated with Mental Well-being and Financial Well-being (each P[B] < 0.05). Equations and examples for calculation of the percentiles are provided. CONCLUSION: Percentiles and effect size estimates are provided to facilitate interpretation of the SCQOLS.

Two valid and reliable short forms of the Singapore caregiver quality of life scale were developed: SCQOLS-10 and SCQOLS-15.

OBJECTIVES: The Singapore Caregiver Quality of Life Scale (SCQOLS) comprises five domains and 51 items in total. This study aimed to develop and evaluate short forms of SCQOLS. STUDY DESIGN AND SETTING: Data were collected from 612 family caregivers of patients with advanced cancers in Singapore. Exploratory factor analysis and best subset regression were used to identify candidate items for each domain. The short forms were evaluated for measurement properties. RESULTS: Inclusion of at least two items per domain in the short form gave correlation coefficients of at least 0.8 with the corresponding domain scores in the full-length version. The short forms and full-length version had similar correlation coefficients with Negative Personal Impact and Positive Personal Impact measures. Two of the five domains of the 10-item version had Cronbach's alpha ≤0.50 and test-retest reliability ≤0.65. A 15-item version of the scale with two to four items per domain performed satisfactorily in all aspects evaluated. CONCLUSION: A 15-item short form of the SCQOLS (SCQOLS-15) is valid and reliable for the assessment of the overall and domain-specific quality of life of family caregivers. A 10-item short form (SCQOLS-10) may serve as a quick, valid and reliable assessment of the overall level of quality of life.

Development and evaluation of a quality of life measurement scale in English and Chinese for family caregivers of patients with advanced cancers.

BACKGROUND: The quality of life of family caregivers of patients with advanced cancers is an important concern in oncology care. Yet, there are few suitable measurement scales available for use in Asia. This study aims to develop and evaluate a locally derived measurement scale in English and Chinese to assess the quality of life of family caregivers of patients with advanced cancers in Singapore. METHODS: Scale contents were generated from qualitative research that solicited inputs from family caregivers. Six hundred and twelve family caregivers of patients with advanced cancers were recruited, of whom 304 and 308 chose to complete the English and Chinese versions of the quality of life scale, respectively. A follow-up survey was conducted for test-retest reliability assessment. Analyses began with pooling all observations, followed by analyses stratified by language samples and ethnic groups (among English-speaking participants). RESULTS: Factor analysis identified 5 domains of quality of life. The Root Mean Square Error of Approximation was 0.041 and Comparative Fit Index was 0.948. Convergent and divergent validity of the total and domain scores were demonstrated in terms of correlation with the Brief Assessment Scale for Caregiver and its sub-scales and a measure of financial concern; known-group validity was demonstrated in terms of differences between groups defined by patient's performance status. Internal consistency (Cronbach's alpha) of the total and domain scores ranged from 0.86 to 0.93. Test-retest reliability (intraclass correlation coefficient) ranged from 0.74 to 0.89. Separate analyses of the English- and Chinese-speaking samples and ethnic groups gave similar results. CONCLUSION: A new, validated, multi-domain quality of life measurement scale for caregivers of patients with advanced cancers that is developed with inputs from family caregivers is now available in two languages. We call this the Singapore Caregiver Quality Of Life Scale (SCQOLS).