title: Small airway disease in asthma: pathophysiological and diagnostic considerations.
abstract: OBJECTIVE
  The aim of the current review is to summarize the evidence of small airway abnormalities in asthma, the proposed diagnostic tools for small airway abnormalities and the clinical implications of small airway abnormalities in asthma.
  
  
  RESULTS
  Pathological abnormalities in the peripheral membranous bronchioles less than 2 mm in diameter (i.e. small airways) can be very frequently detected in asthma patients across severity: from mild to the more severe clinical manifestations of the disease. Interestingly, not only are small airway abnormalities present in asthma, but there is evidence that the magnitude of small airway abnormalities correlates with the severity of the disease. So far no unanimously accepted method and/or algorithm is available for small airway abnormality detection; however, some functional techniques and inflammatory markers have been used as surrogates of small airway dysfunction.
  
  
  CONCLUSIONS
  Clinicians, and not only researchers, must consider small airways when approaching asthma patients, particularly when dealing with patients with a 'difficult-to-treat phenotype'. The identification of subgroups of asthma patients with prominent small airway disease is not merely speculative, and carries pathophysiological and therapeutic implications.
authors.affiliation: aSection of Internal and Cardio-Respiratory Medicine, Department of Medical Sciences, Research Centre on Asthma and COPD, University of Ferrara, Ferrara bDipartimento di Scienze della Salute, Pneumologia Riabilitativa, Fondazione Salvatore Maugeri, Istituto Scientifico di Milano IRCCS, University of Milan, Milan, Italy.
authors.forename: Marco
authors.initials: M
authors.lastname: Contoli
authors.forename: Pierachille
authors.initials: P
authors.lastname: Santus
authors.forename: Alberto
authors.initials: A
authors.lastname: Papi
mesh_terms: D000403:Airway Resistance; D001249:Asthma / Q000175:diagnosis* / Q000503:physiopathology*; D055745:Bronchioles / Q000473:pathology*; D018450:Disease Progression; D006801:Humans; D007249:Inflammation / Q000175:diagnosis / Q000503:physiopathology; D010641:Phenotype; D012307:Risk Factors; D012720:Severity of Illness Index; D013147:Spirometry