Prognostic signficance of parental reports of "asthma" and "wheeze" in kindergarten children

Abstract

Objective:Many epidemiological studies of “asthma” and “wheeze” in children rely on parental report of a doctor’s diagnosis and symptoms for identifying cases. We investigated whether parental report of asthma and of wheeze in the Longitudinal Study of Australia Children (LSAC) had any independent prognostic significance in predicting risk of poorer health outcomes and hence whether they could be considered valid markers of disease in children. Methods:Children with or without parent-reported wheeze that lasted for a week or more in the last 12 months and/or parent-reported ever doctor-diagnosed asthma were identified from Wave 1 of the LSAC kindergarten cohort. Outcomes assessed at 2-year follow-up (i.e. Wave 2) were urgent health care utilisation (defined as one or more of: any hospitalisations or ED attendances [ascertained from parental interview] or > 6 visits to a GP [ascertained from MBS data linkage] in the 12 months before the follow-up interview); fair/poor general health status; large/moderate sleeping problems; and 4+ days absent from school in the four school weeks before the follow-up interview. Excluding children with missing data for any of the variables of interest, we used logistic regression with adjustment for the clustered survey design (Proc Surveylogistic, SAS version 9.2) to calculate odds ratios. Later we will compare these results with those based on an imputed dataset created by undertaking multiple imputation using Markov Chain Monte Carlo imputation (Proc MI and Proc MIAnalyse) so that all subjects are retained in the analysis, thereby minimising bias due to missing data. Results:In the complete-subject analysis, among the 489 children with wheeze at Wave 1, parental report that the child had ever been diagnosed with asthma was not associated with increased risk of poor outcomes at Wave 2. However, among the 719 children who had ever been diagnosed with asthma at Wave 1, those who also had wheeze had a significantly higher risk at follow-up of urgent health care utilisation in the last 12 months (OR=1.52); having had 4+ days away from school in the last 4 weeks (OR=1.81); and possibly of having fair/poor health status (OR=1.93 but not statistically significant). Conclusions:Our results do not support the hypothesis that a doctor’s diagnosis of asthma is useful for distinguishing between wheezing syndromes in childhood. In contrast, amongst children with diagnosed asthma, as expected, those with current wheeze had worse health outcomes than those without current wheeze. Acknowledgements: ACAM is an Australian Institute of Health and Welfare collaborating unit, funded by the Australian Government Department of Health and Ageing.