Espettorato indotto e patologie dell'apparato respiratorio

Induced sputum is a nonivasive technique useful to assess airway inflammation. Sputum is induced through the inhalation of ultrasonic nebulized hypertonic saline solution and pre-treatment of the subject with b2 agonist is recommended to avoid bronchoconstriction. After the inhalation period the subject is invited to cough and to produce sputum. The sample is sent to the laboratory within 2 hours where it is solubilised in order to evaluate total cells and differential inflammatory cell count. Sputum of a healthy subject is mainly constituted by macrophages and neutrophils while eosinophils, lymphocytes and epithelial cells are only rarely present. Most asthmatic subjects have an increase of eosinophils in their sputum samples but neutrophilic or paucigranular patterns are also found in asthmatics' airways. Sputum eosinophils are usually predictors of a good response to inhaled or systemic corticosteroid therapy, whereas the presence of neutrophils in induced sputum, suggests a different therapeutic choice since neutrophils are not responsive to steroids. Furthermore, neutrophils are the most represented inflammatory cells in the sputum samples of subjects with chronic obstructive pulmonary disease (COPD). Total cells and sputum neutrophils increase during disease exacerbation. In the sputum of COPD subjects, the presence of eosinophils can precede an exacerbation and envisages a favourable response to steroids. Soluble mediators can be measured in the supernatant of processed induced sputum samples, particularly many cytokines, chemokines and other markers of inflammation and oxidative stress, but none of them seems to be particularly useful for the diagnosis or for the follow-up of patients with respiratory diseases. The majority of studies on induced sputum are conducted on asthmatic and COPD subjects but the scarce invasiveness of the procedure also allows its application in other pulmonary diseases such as eosinophilic bronchitis, cystic fibrosis, interstitial lung diseases.