Is the childhood asthma questionnaire a good measure of health-related quality of life of asthmatic children in Asia?: validation among paediatric patients with asthma in Singapore.

BACKGROUND

Health-related quality of life (HR-QOL) is an important outcome in the treatment of chronic childhood diseases such as asthma. However, this measure is rarely used in young children in Asia because of the difficulty of obtaining valid, reliable instruments that are developmentally and culturally suitable.

OBJECTIVES

To select, culturally adapt and validate a disease-specific HR-QOL questionnaire (Childhood Asthma Questionnaire [CAQ]-B) for asthmatic children aged 7-11 years in Singapore, and to understand the relationship between patient-reported HR-QOL domains and physician- or caregiver-rated severity.

METHODS

A literature review was conducted to shortlist questionnaires based on pre-specified criteria. A pre-test was conducted to assess suitability and relevance of the questionnaires in Singapore. The selected questionnaire (CAQ-B) was then adapted to more closely reflect the local culture, climate, school system and terminology. Cross-sectional validation was conducted. All asthmatic patients aged 7-11 years attending the respiratory clinic in a paediatric hospital, and without co-morbidities that could significantly affect their HR-QOL, were invited to participate. Patients and their parents or caregivers were asked to complete the relevant sections of the questionnaire before their medical consultation. The child's severity of asthma was rated by the attending physician according to guidelines from the Singapore Ministry of Health. Correlations between the child-reported CAQ-B outcomes and clinical ratings of severity by both parents and physicians were investigated. Internal reliability was tested with Cronbach's alpha, and the overall questionnaire structure was explored using principal axis analysis with oblimin rotation and extraction for factors with Eigen values >1.0.

RESULTS

The adapted CAQ-B was validated in 96 patients (40 girls and 56 boys) with a mean age of 8.7 +/- 1.1 years (range 7-11). Most children had no difficulty understanding and completing the questionnaire. The median time taken to complete a questionnaire was 10 minutes. Internal consistency of the various scales ranged from 0.29 to 0.76 (Cronbach's alpha) when items were analysed according to the UK or Australian scale structure. This increased to 0.57-0.76 after item reduction. Physician-rated severity only correlated significantly with the Active Quality of Living (AQOL) domain (r = -0.29, p = 0.02). However, parent/caregiver-rated severity correlated with three of four patient-reported domains: AQOL (r = -0.359, p = 0.001), Passive Quality Of Living (PQOL) [r = -0.271, p < 0.01] and severity (r = 0.367, p < 0.001). The AQOL domain was significantly correlated with the PQOL domain (r = 0.513, p = 0.005).

CONCLUSIONS

The children and parents/caregivers in this study found CAQ-B to be a simple and acceptable questionnaire with some evidence of content validity. While two of the domains did not meet internal consistency standards expected of HR-QOL instruments for adults (Cronbach's alpha = 0.70), they were acceptable for children of this age. The patterns of correlation also suggest that parent/caregivers' perception of the severity of a young child's asthma may be a better indicator of a child's HR-QOL than clinical diagnosis of severity. However, further investigation is recommended to improve and validate the internal structure of the scale.