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

We must address our limitations. Firstly, nasal swab were not collected in 45 out of 211 of episodes that met the criteria for unscheduled visits. For the extreme case scenario whereby all these 45 episodes were asthma exacerbations with viruses isolated, the virus detection rate would have been 56.2 % but this is still much lower than Southampton study. For the remaining 94 episodes of mild respiratory illnesses that did not meet the criteria for unscheduled visit, it was difficult to ascertain whether the subjects actually had very mild asthma exacerbations, leading to a possible underestimation. The second limitation was that nasal swab instead of nasopharyngeal aspirate was used for infection control reasons as the study was carried out in the immediate post-SARS period. A recent study also showed that the sensitivity of nasal swabs was comparable to that of nasopharyngeal aspirates for the detection of all major respiratory viruses except RSV [11] . Yet, RSV virus is not a common trigger of asthma exacerbations in school-aged children. The use of a flocked nasopharyngeal swab, which was not available at time of the study, can certainly lead to a better yield should similar study to be conducted in the future [4] .