This cross-sectional emergency department study of 70 wheezing children and 59 control subjects (2 mo to 16 yr of age) examined the prevalence of respiratory viruses and their relationship to age, atopic status, and eosinophil markers. Nasal washes were cultured for respiratory viruses, assayed for respiratory syncytial virus (RSV) antigen, and tested for coronavirus and rhinovirus RNA using reverse transcription-PCR (RT-PCR). Also evaluated were eosinophil numbers and eosinophil cationic protein (ECP) in both nasal washes and serum, along with total IgE and specific IgE antibody in serum. Respiratory viruses were detected in 82% (18 of 22) of wheezing infants younger than 2 yr of age and in 83% (40 of 48) of older wheezing children. The predominant pathogens were RSV in infants (detected in 68% of wheezing subjects) and rhinovirus in older wheezing children (71%), and both were strongly associated with wheezing (p < 0.005). RSV was largely limited to wheezing children younger than 24 mo of age, but rhinovirus was detected by RT-PCR in 41% of all infants and in 35% of nonwheezing control subjects older than 2 yr of age. After 2 yr of age the strongest odds for wheezing were observed among those who had a positive RT-PCR test for rhinovirus together with a positive serum radioallergosorbent testing (RAST), nasal eosinophilia, or elevated nasal ECP (odds ratios = 17, 21, and 25, respectively). Results from this study demonstrate that a large majority of emergent wheezing illnesses during childhood (2 to 16 yr of age) can be linked to infection with rhinovirus, and that these wheezing attacks are most likely in those who have rhinovirus together with evidence of atopy or eosinophilic airway inflammation.

Asthma is a disease characterized by chronic inflammation and reversible obstruction of the small airways resulting in impaired pulmonary ventilation. Hyperpolarized 3 He magnetic resonance (MR) lung imaging is a new technology that provides a detailed image of lung ventilation. Hyperpolarized 3 He lung imaging was performed in 10 asthmatics and 10 healthy subjects. Seven asthmatics had ventilation defects distributed throughout the lungs compared with none of the normal subjects. These ventilation defects were more numerous and larger in the two symptomatic asthmatics who had abnormal spirometry. Ventilation defects studied over time demonstrated no change in appearance over 30 -60 minutes. One asthmatic subject was studied twice in a three-week period and had ventilation defects which resolved and appeared in that time. This same subject was studied before and after bronchodilator therapy, and all ventilation defects resolved after therapy. Hyperpolarized 3 He lung imaging can detect the small, reversible ventilation defects that characterize asthma. The ability to visualize lung ventilation offers a direct method of assessing asthmatics and their response to therapy. J. Magn. Reson. Imaging 2001;13: 378 -384.

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Background-The amount of allergen necessary to sensitise genetically "at risk" children is unclear. The relation between allergen exposure and asthma is also uncertain. Methods-To ensure a wide range of allergen exposures the data from case-control studies of asthma in children aged 12-14 years attending three schools in Los Alamos, New Mexico and Central Virginia were combined. Skin prick tests to indoor and outdoor allergens and bronchial hyperreactivity to histamine were assessed in children with and without symptoms of asthma. The concentration of mite, cat, and cockroach allergens in dust from the children's homes was used as a marker of exposure. Results-Three hundred and thirty two children (157 with asthmatic symptoms and 175 controls) were investigated. One hundred and eighty three were classified as atopic on the basis of allergen skin prick tests and 68 as asthmatic (symptoms plus bronchial responsiveness). The prevalence and degree of sensitisation to mite and cockroach, but not cat, was strongly associated in atopic children with increasing domestic concentrations of these allergens. Asthma was strongly associated with sensitisation to indoor allergens (p<10 -6 ) and weakly to outdoor allergens (p = 0.026). There was an association between current asthma and the concentration of mite allergen amongst atopic children (p = 0.008) but not amongst those who were specifically mite sensitised (p = 0.16). Conclusions-The domestic reservoir concentration of mite and cockroach, but not cat, allergen was closely related to the prevalence of sensitisation in atopic children. However, the prevalence of current asthma had a limited relationship to these allergen measurements, suggesting that other factors play a major part in determining which allergic individuals develop asthma. (Thorax 1999;54:675-680)

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