Is it time for a simplified method to evaluate airway eosinophilia?

Extract Evaluation of sputum cells is a standardised methodology useful to assess airway inflammation. When patients are able to expectorate, spontaneous sputum can be analysed [1], while, if this does not occur, sputum can be induced with the inhalation of hypertonic saline solution. Induction and processing of sputum samples are standardised methodologies and guidelines were published many years ago in order to ensure uniform application [2–4]. Sputum cell percentages are the most useful data, from the clinical point of view, that we can obtain from sputum samples. Reference values in healthy controls with different age ranges were published and reproducibility of the data, particularly of neutrophils and eosinophils, was demonstrated [5–8]. Aligning with the type of cells present in the airways, different inflammatory phenotypes have been distinguished: eosinophilic, neutrophilic, mixed granulocytic or paucigranulocytic [9, 10].