ASTHMA

Heterogeneity of asthma according to blood inflammatory patterns

R Nadif¹, V Siroux², M-P Oryszczyn¹, C Ravault¹, C Pison¹, I Pin³, F Kauffmann¹ on behalf of the Epidemiological study on the Genetics and Environment of Asthma (EGEA)

¹ INSERM, U780, Epidemiology and Biostatistics, and Université Paris-Sud, IFR69, Villejuif, France
² INSERM, U823, Epidemiologie des cancers et des affections graves, Centre de Recherche Albert Bonniot, and Université Joseph Fourier, Grenoble, France
³ CHU Grenoble, Pédiatrie, and INSERM, U823, Grenoble, France

Mrs R Nadif, Institut National de la Santé et de la Recherche Médicale, Recherche en Epidémiologie et Biostatistique U780-IFR69, 16 avenue Paul Vaillant Couturier, 94807 Villejuif cedex, France; rachel.nadif{at}inserm.fr

Rationale: There is increasing interest regarding asthma heterogeneity in relation to inflammatory patterns.

Objectives: To assess phenotypic characteristics, in particular clinical presentation of the disease, in 381 well-characterised adults with asthma from the French Epidemiological study on the Genetics and Environment of Asthma (EGEA) according to their blood inflammatory pattern.

Methods: Four blood inflammatory patterns were defined according to eosinophil (EOS) and neutrophil (NEU) count cut-off points. Samples with 250 EOS/mm³ were classified as EOS^hi and those with 5000 NEU/mm³ as NEU^hi. Clinical characteristics include typical asthma and chronic obstructive pulmonary disease (COPD)-like symptoms, as well as composite quantitative scores addressing the activity of the disease.

Results: A substantial number of those with asthma (56.2%) had the EOS^lo pattern (<250 EOS/mm³). Patients with asthma who had the EOS^hi pattern had higher immunoglobulin E (IgE), a lower forced expiratory volume in 1 s (FEV₁) and presented a more active asthma than those with the EOS^lo pattern. Among those with the EOS^lo pattern, neutrophil inflammation (NEU^hi) was related to a less frequent positive skin prick test response (OR 0.44, 95% CI 0.20 to 0.96). Among those with the EOS^hi pattern, neutrophil inflammation did not explain current asthma or asthma activity, and was significantly related to nocturnal symptoms (OR 5.21, 95% CI 1.44 to 18.8) independently of age, sex, smoking and inhaled corticosteroid treatment. In non-smokers with asthma, COPD-like symptoms, in particular chronic phlegm, were more frequent in those with neutrophil inflammation, independent of eosinophil inflammation (OR 2.35, 95% CI 1.08 to 5.10).

Conclusions: Besides eosinophilia, neutrophil inflammation assessed in the blood is related to specific characteristics of asthma. Considering simultaneously neutrophilic and eosinophilic inflammation may contribute to help to disentangle this complex disease.

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