Objective
Although bronchiolitis is generally considered a single disease, recent studies suggest heterogeneity. We aimed to identify severe bronchiolitis profiles using a clustering approach.
Methods
We analyzed data from two prospective, multi-center cohorts of children younger than 2 years hospitalized with bronchiolitis, one in the U.S. (2007–2010 winter seasons, n=2,207) and one in Finland (2008–2010 winter seasons, n=408). Severe bronchiolitis profiles were determined by latent class analysis, classifying children based on clinical factors and viral etiology.
Results
In the U.S. study, four profiles were identified. Profile A (12%) was characterized by history of wheezing and eczema, wheezing at the ED presentation and rhinovirus infection. Profile B (36%) included children with wheezing at the ED presentation, but, in contrast to profile A, most did not have history of wheezing or eczema; this profile had the largest probability of RSV-infection. Profile C (34%) was the most severely ill group, with longer hospital stay and moderate-to-severe retractions. Profile D (17%) had the least severe illness, including non-wheezing children with shorter length-of-stay. Two of these profiles (A and D) were replicated in the Finnish cohort; a third group (“BC”) included Finnish children with characteristics of profiles B and/or C in the U.S. population.
Conclusion
Several distinct clinical profiles (phenotypes) were identified by a clustering approach in two multicenter studies of children hospitalized for bronchiolitis. The observed heterogeneity has important implications for future research on the etiology, management and long-term outcomes of bronchiolitis, such as future risk of childhood asthma.