title: Asthma-COPD overlap 2015: now we are six.
abstract: BACKGROUND
  The overlap between asthma and COPD is increasingly recognised. This review examines the new insights, treatment and remaining knowledge gaps for asthma-COPD overlap.
  
  
  METHODS
  A systematic literature review of cluster analyses of asthma and COPD was performed. Articles from 2009 to the present dealing with prevalence, morbidity and treatment of asthma-COPD overlap were identified and reviewed.
  
  
  RESULTS
  Asthma-COPD overlap was consistently recognised in studies using a variety of different study designs and sampling. The prevalence was approximately 20% in patients with obstructive airways diseases. Asthma-COPD overlap was associated with increased morbidity and possibly an increased mortality and comorbidity. There was evidence of a heterogeneous pattern of airway inflammation that included eosinophilic (in adult asthma), neutrophilic or mixed patterns (in severe asthma and COPD). Systemic inflammation was present in asthma-COPD overlap and resembled that of COPD. Within asthma-COPD overlap, there is evidence of different subgroups, and recognition using bronchodilator responsiveness has not been successful. Guidelines generally recommend a serial approach to assessment, with treatment recommendations dominated by an asthma paradigm. Research is needed into key clinical features that impact outcome, mechanisms and treatment approaches in asthma-COPD overlap. Identifying and treating disease components by multidimensional assessment shows promise.
  
  
  CONCLUSIONS
  Asthma-COPD overlap has drawn attention to the significant heterogeneity that exists within obstructive airway diseases. It should be replaced by novel approaches that identify and manage the components of this heterogeneity, such as multidimensional assessment and treatment. Future research is needed to test these novel and personalised approaches.
authors.affiliation: Priority Research Centre for Asthma and Respiratory Diseases, University of Newcastle, Newcastle, New South Wales, Australia Department of Respiratory and Sleep Medicine, John Hunter Hospital, New Lambton Heights, New South Wales, Australia.
authors.forename: Peter G
authors.initials: PG
authors.lastname: Gibson
authors.affiliation: Priority Research Centre for Asthma and Respiratory Diseases, University of Newcastle, Newcastle, New South Wales, Australia Department of Respiratory and Sleep Medicine, John Hunter Hospital, New Lambton Heights, New South Wales, Australia.
authors.forename: Vanessa M
authors.initials: VM
authors.lastname: McDonald
mesh_terms: D001249:Asthma / Q000097:blood / Q000175:diagnosis / Q000453:epidemiology* / Q000628:therapy; D015415:Biomarkers / Q000097:blood; D016000:Cluster Analysis; D015897:Comorbidity; D006801:Humans; D018836:Inflammation Mediators / Q000378:metabolism; D017410:Practice Guidelines as Topic; D015995:Prevalence; D029424:Pulmonary Disease, Chronic Obstructive / Q000097:blood / Q000175:diagnosis / Q000453:epidemiology* / Q000628:therapy; D013577:Syndrome
chemical_list: D015415:Biomarkers; D018836:Inflammation Mediators
keywords: Asthma; Asthma Guidelines; COPD epidemiology; Paediatric asthma