Eosinophil protein X and childhood asthma: A systematic review and meta-analysis

BACKGROUND: There are no reference guidelines for health care providers regarding appropriate use and interpretation of urine eosinophil protein X (u-EPX) in clinical practice. Currently, there are no clear-cut clinical or laboratory parameters to diagnose asthma in young children.

OBJECTIVE: In this study, we (1) systematically reviewed and qualitatively appraised the epidemiological evidence to determine diagnostic u-EPX cut points for pediatric asthma, and (2) performed a meta-analysis to provide u-EPX estimates for diagnosing pediatric asthma.

METHODS: Research articles in literature were identified from PubMed/Medline and Web of Science databases from 1966 to August 2015. Children <18 years of age were included. Both serum and urine EPX were included. Twenty-seven studies met the inclusion criteria for the systematic review and nine studies for the meta-analysis. Details regarding EPX analyses, treatment efficacy, and outcomes were assessed. For meta-analyses, effect estimates were abstracted using standardized means.

RESULTS: Over 70% of studies found a significant relationship between u-EPX and childhood asthma. There was 1.94 times higher standardized means of u-EPX among acute asthmatics compared to healthy controls (confidence interval [CI]: 1.67-2.22). Similarly, the difference in standardized means between asymptomatic asthmatics and healthy controls was 1.58 times higher (CI: 1.27-1.88).

CONCLUSIONS AND CLINICAL RELEVANCE: Despite differences in sample sizes, EPX processing and measurement, and ages of children, a consistent trend of higher EPX levels with childhood asthma was revealed.