title: Bronchial hyperresponsiveness.
abstract: BACKGROUND
  Bronchial hyperresponsiveness (BHR) is often regarded as a 'hallmark' of asthma and bronchoprovocation testing is frequently performed to support a diagnosis of asthma. However, BHR is also found in a spectrum of other lung diseases and can be provoked by a variety of specific stimuli.
  
  
  OBJECTIVE
  To review the pathophysiology of BHR, discuss various methods of testing for BHR and describe the epidemiology of BHR in a variety of previously studied populations.
  
  
  METHODS
  We performed a systematic review of references identified using Medline and hand searches of identified articles. Because of space limitations, we have included those reports that seem most representative of the overall BHR literature.
  
  
  RESULTS
  BHR can be induced by a variety of stimuli that trigger a number of different but overlapping physiological mechanisms. Bronchoprovocation testing can be performed using a variety of stimuli, various protocols and differing test criteria, yielding results that may be discordant. Elevated rates of BHR have been reported in studies of smokers, chronic obstructive pulmonary disease patients, atopics, athletes, exposed workers and the general population.
  
  
  CONCLUSIONS
  Due to the prevalence of BHR in a spectrum of clinical patients and working populations, clinicians should be aware that BHR is not specific for asthma. When performed correctly, the greatest clinical value of BHR testing is to rule out suspected asthma in patients in whom testing is negative. Assessment of BHR also provides insights into the pathological mechanisms of airway disease.
authors.affiliation: Department of Environmental Health Sciences, Yale School of Public Health, Yale University, New Haven, CT 06510, USA, Department of Internal Medicine (Yale Occupational and Environmental Medicine Program), Yale School of Medicine, Yale University, New Haven, CT 06510, USA. jonathan.borak@yale.edu.
authors.forename: J
authors.initials: J
authors.lastname: Borak
authors.affiliation: Department of Internal Medicine (Yale Occupational and Environmental Medicine Program), Yale School of Medicine, Yale University, New Haven, CT 06510, USA.
authors.forename: R Y
authors.initials: RY
authors.lastname: Lefkowitz
mesh_terms: D001249:Asthma / Q000175:diagnosis* / Q000503:physiopathology; D016535:Bronchial Hyperreactivity / Q000175:diagnosis* / Q000503:physiopathology; D001985:Bronchial Provocation Tests / Q000379:methods*; D001993:Bronchodilator Agents / Q000627:therapeutic use; D018450:Disease Progression; D006801:Humans; D009784:Occupational Diseases / Q000175:diagnosis* / Q000503:physiopathology; D016273:Occupational Exposure / Q000009:adverse effects*; D015995:Prevalence; D012907:Smoking / Q000009:adverse effects*
chemical_list: D001993:Bronchodilator Agents
keywords: Airway hyperresponsiveness; BHR; asthma; bronchoprovocation; histamine; methacholine; occupational asthma; spirometry.