Is respiratory viral infection really an important trigger of asthma exacerbations in children?

Lee, So-lun; Chiu, Shui-seng Susan; Malik, Peiris Joseph S.; Chan, Kwok-hung; Wong, Hing-sang Wilfred; Lau, Yu-lung

Previous studies showed virus identification rate ranged from 32% to 85% of asthma exacerbation in children [14, 19] . The conservative estimation of virus detection rate of 50% would give the largest sample size estimate of 96 exacerbations with level of confidence at 95% and precision of detection rate of 10%. As the number of urgent visits due to asthma was 1.2 per person-year in children on regular inhaled steroids in another study, the number of subjects required would be around 80 [22] . We performed simple descriptive analyses of demographic data. The frequencies of presenting symptoms and physician diagnoses of unscheduled visits, virus detection rate and the distribution of different types of viruses were described. Student T test (+− Mann-Whitney U test) was used to compare continuous variables; for example, age and Pearson's chi-square test (with Yates'correction/Fisher's exact test) was used to compare categorical variables; for example, sex (female or male), atopic status (yes or no) between children with and without unscheduled visits. A p value less than 0.05 was considered to be statistically significant. All statistical analyses were carried out by the SPSS 11.0 software (SPSS Inc., Chicago, IL).