The components and time line of the subject visits are outlined in Table 2 Mothers underwent prick skin testing to eight common aeroallergens and a blood specimen was obtained by venepuncture for serum immunoglobulin E (IgE) and DNA. A structured abstraction form was used to obtain information from the medical record regarding the index enrolment visit: current infant weight, confirmation of birth weight, room air pulse oximetry, requirement for supplemental oxygen, medication administration, prior wheezing episodes and detailed information on the current illness and hospital course. Following discharge from the hospital or outpatient setting, the final discharge diagnosis and results of culture data were obtained through chart review.