Past asthma exacerbation in children predicting future exacerbation: a systematic review

Acute exacerbations are common in children and potentially preventable. Currently, a past exacerbation is the best predictor of a future exacerbation. We undertook a systematic review of the literature describing the relationship between past and future exacerbations. Our analysis considered whether the odds ratios for one exacerbation to predict a recurrence were different across different categories of exacerbation. Four databases were searched systematically (MEDLINE, Embase, the Cumulative Index to Nursing and Allied Health and PsycInfo). Exacerbations were categorised by severity as: presentation to emergency department (ED); hospital admission; paediatric intensive care unit (PICU) admission; and "unspecified severity" (i.e. no distinction between severity categories was made). Meta-analysis was performed for studies where sufficient data were provided for inclusion. There were 26 eligible articles from 9185 identified. There was significant heterogeneity in duration of follow-up, healthcare system and exacerbation definition between studies. For the unspecified severity definition, the odds ratio for an exacerbation after a previous exacerbation was 9.87 (95% CI 5.02-19.39; six studies, 162 583 individuals). PICU admission was also associated with increased risk of future admission (OR 5.87, 95% CI 2.96-11.64; two studies, 730 individuals). Meta-analysis was not possible for ED visits or hospitalisation. The median odds ratio (range) for past ED visit predicting future ED visit was 6.27 (3.3-8.26) and for past hospitalisation predicting future hospitalisation was 3.37 (1.89-5.36). The odds for a second asthma exacerbation do not necessarily increase with increasing severity of an initial exacerbation.