Respiratory syncytial virus infection in children hospitalized for wheezing:: Virus-specific studies from infancy to preschool years

Aim: To evaluate whether the presence of immunoglobulin G (IgG) antibodies against respiratory syncytial virus (RSV) in early childhood is associated with later asthma, and to evaluate a new diagnostic test for RSV, reverse-transcription polymerase chain reaction (RT-PCR), comparing it to the antigen and antibody assays initially used in RSV diagnostics in the present cohort. Methods: At the start of the study in 1992-1993, RSV was studied by antigen detection (using time-resolved fluoroimmunoassay) and complement-fixing antibody assay. Advances in methodology allowed us to supplement RSV studies by RT-PCR in frozen nasopharyngeal aspirates obtained on admission, and by specific IgG antibodies (using enzyme immunoassay) in frozen serum samples obtained during the follow-up. Results: On admission, 29 of the 100 children hospitalized for wheezing at <2 y of age were RSV positive. When compared with conventional methods, the sensitivity of RT-PCR was 83% (100% w.r.t. antigen detection) and its specificity was 92% in diagnosing RSV infection. RSV-specific IgG antibody concentrations rose with age, but were not predictive of asthma at any age. In the present cohort, wheezing without RSV was particularly associated with increased risk for later childhood asthma. Conclusion: Hospitalization for wheezing in infancy is associated with increased risk for later childhood asthma, particularly in children without RSV infection on admission, although children with RSV have also slightly increased risk for later asthma. However, mere serological evidence of RSV infection is not associated with the development of asthma. In addition to RSV, more attention should be paid to less virulent agents in order to find those wheezing infants who are at particular risk of later childhood asthma.