Temporal stability of multiple trigger and episodic viral wheeze in early childhood

The distinction between episodic viral wheeze (EVW) and multiple trigger wheeze (MTW) is used to guide management of preschool wheeze. It has been questioned whether these phenotypes are stable over time. We examined the temporal stability of MTW and EVW in two large population-based cohorts. We classified children from the Avon Longitudinal Study on Parents and Children (N=10,970) and the Leicester Respiratory Cohorts (LRC, N=3,263) into EVW, MTW and no wheeze at ages 2, 4 and 6 years based on parent-reported symptoms. Using multinomial regression, we estimated relative risk ratios (RRRs) for EVW and MTW at follow-up (no wheeze as reference category) with and without adjusting for wheeze severity. Although large proportions of children with EVW and MTW became asymptomatic, those that continued to wheeze showed a tendency to remain in the same phenotype: Among children with MTW at 4 years in LRC the adjusted RRR was 15.6 (95% CI: 8.3, 29.2) for MTW (stable phenotype) compared to 7.0 (2.6, 18.9) for EVW (phenotype switching) at 6 years. The tendency to track was weaker for EVW and from 2-4 years. Results were similar across cohorts. This suggests that MTW and, to a lesser extent, EVW track regardless of wheeze severity.