Subtype prevalence and treatment implication in adolescents and adults with mild-to-moderate asthma: Systematic review and meta-analysis

Abstract

BackgroundInhaled corticosteroid (ICS) containing regimens are the mainstay for treating asthma despite usually being ineffective in non-eosinophilic asthma (NEA). Data on the prevalence of NEA versus eosinophilic asthma (EA) in mild-to-moderate asthmatics is limited. ObjectiveTo systematically review the subtype prevalence of mild-to-moderate asthma in adolescents and adults using sputum inflammatory cell analysis and their responses to ICS. MethodsWe searched electronic databases (PubMed, Scopus, EMBASE, Cochrane) for studies in adolescents and adults with mild-to-moderate asthma. The primary outcome was the prevalence of asthma subtypes based on sputum inflammatory cell analysis, categorized into EA and NEA. The secondary outcome involved comparing asthma outcomes between different subtypes following ICS therapy. Certainty of evidence was reported for each pooled analysis. ResultsEighteen studies involving 3,533 adolescents and adults with mild-to-moderate asthmatics were reviewed. The pooled prevalence (95% confidence interval, CI) of NEA was estimated at 40.39% (27.54, 53.93) in patients with ICS naïve with very low certainty of evidence. Upon reevaluating sputum cytology, approximately 20% to 30% of patients initially classified as having NEA transitioned to the EA subtype. EA patients showed significant improvements in asthma symptoms, FEV1 [standardized mean difference (95% CI): 0.79 (0.30, 1.27)], and airway hyperresponsiveness [1.34 (0.29, 2.40)] following ICS therapy, while NEA patients exhibited limited response. ConclusionA high proportion of adolescents and adults with mild-to-moderate asthma were identified as having the NEA subtype, which exhibited a poor response to ICS. A thorough diagnostic evaluation before initiating treatment should be integrated into clinical practice.