Source: International Congress 2014 – Phenotyping and monitoring asthma and COPD
Disease area: Airway diseases

Abstract

Rationale: Sputum inflammometry has been used to phenotype asthma, with eosinophilic, neutrophilic, mixed granulocytic and paucicellular sub-groups described. Both ³40% and ³61% have been used as criteria to define sputum neutrophilia.Methods: As part of the Wessex Severe Asthma Cohort study, induced sputum was obtained from healthy non-asthmatic controls (HC, n=67), non-steroid treated asthmatics (MA , n=44), steroid treated (step 2/3) asthmatics (ModA, n=44) and those with severe (step 4/5 treated)asthma (SA, n=246) and differential cell counts obtained. Sputum neutrophil counts were not normally distributed and group comparisons were undertaken using non-parametric statistical analysis.Results: Median [1QR] sputum neutrophil % was significantly greater (p<0.001) in the SA (51.0 [38.7] than either HC (19.3 [31.50], p<0.0001), MA (25.40 [31.37], p<0.0001) or ModA (31.05 [41.70], p=0.005). ModA neutrophil % was significantly higher than HC (p<0.02) but not MA. The respective proportion of subjects (%) with neutrophil % of ³40% and ³61% was: SA (65.4 and 39.4), ModA (43.2 and 22.7), MA (31.8 and 15.9), HC (25.4 and 12.9). In SA neutrophil% in sputum was independent of smoking history, atopic status or oral steroid use and very weakly correlated with age and FEV1% predicted (inverse) (each R2 = 0,031, p=0.005). Sputum eosinophilia (³2%) was evident in 34.8% and 29.9% of those with³40% and ³61%sputum neutrophilia respectively.Conclusion: Neutrophilic asthma is a prominent phenotype in severe asthma with approximately one third also having co-existent airway eosinophilic inflammation independent of the definition.Funding: WSAC was funded by the Medical Research Council UK.

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C. Barber, S. Elliott, J. Ward, L. Lau, K. Gove, T. Brown, H. Rupani, T. Hinks, R. Djukanovic, R. Kurukuaaratchy, A. Chauhan, P. Howarth (Southampton, Portsmouth, United Kingdom). Sputum neutrophil differential cell count in health and relationship to disease severity in asthma. Eur Respir J 2014; 44: Suppl. 58, 1691

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