Asthma inflammatory phenotypes on four continents:the World Asthma Phenotypes (WASP) international collaboration

The World Asthma Phenotypes (WASP) study is being conducted in five centres in Brazil, Ecuador, Uganda, New Zealand and the United Kingdom, with a range of prevalence levels and exposures, and a likely range of phenotype distributions. Here we present the main findings with regards to inflammatory phenotypes. We recruited 998 cases and 356 controls: 204/40 in Brazil, 176/67 in Ecuador, 207/50 in Uganda, 235/132 in New Zealand, and 176/67 in the United Kingdom. All centres studied children and adolescents, with the exception of the UK centre which involved 26-27 year olds. The proportions of participants who produced sputum samples was 84%, with a range from 74% (Brazil) to 91% (Ecuador), and of these 77% were countable with regards to the inflammatory cell types.The proportions of asthma cases who were classified as eosinophilic or mixed granulocytic asthma (the two inflammatory phenotypes which involve eosinophilia, based on >x.x% of cells being eosinophils) was 37% overall: 35% in Brazil, 32% in Ecuador, 33% in Uganda, 48% in New Zealand, and 28% in the United Kingdom. The non-eosinophilic asthmatics (NEA) had similar severity (e.g. in terms of attacks in the previous year) to the eosinophilic asthmatics (EA). Of the 62% of cases with NEA, 51% showed no signs of inflammation (paucigranulocytic), with 11% having neutrophilic inflammation. This is the first time that sputum induction has been used in a standardised manner to compare asthmatics in high income countries (HICs) and low-and-middle-income countries (LMICs). It confirms previous research in HICs that only about one-half of current asthmatics have EA, and it shows for the first time that only about one-third of asthmatics in the centres in LMICs have EA.