title: The prevalence of severe refractory asthma.
abstract: BACKGROUND
  Severe asthma is characterized by difficulty to achieve disease control despite high-intensity treatment. However, prevalence figures of severe asthma are lacking, whereas longstanding estimates vary between 5% and 10% of all asthmatic patients. Knowing the exact prevalence of severe refractory asthma as opposed to difficult-to-control asthma is important for clinical decision making, drug development, and reimbursement policies by health authorities.
  
  
  OBJECTIVE
  We sought to estimate the prevalence of severe refractory asthma as defined by the Innovative Medicine Initiative consensus.
  
  
  METHODS
  Adult patients with a prescription for high-intensity treatment (high-dose inhaled corticosteroids and long-acting β2-agonists or medium- to high-dose inhaled corticosteroids combined with oral corticosteroids and long-acting β2-agonists) were extracted from 65 Dutch pharmacy databases, representing 3% of the population (500,500 inhabitants). Questionnaires were sent to 5,002 patients, of which 2,312 were analyzed. The diagnosis of asthma and degree of asthma control were derived from questionnaires to identify patients with difficult-to-control asthma. Inhalation technique was assessed in a random sample of 60 adherent patients (prescription filling, ≥80%). Patients with difficult-to-control asthma, adherence to treatment, and a correct inhalation technique were qualified as having severe refractory asthma. Results were mirrored to the Dutch population.
  
  
  RESULTS
  Of asthmatic adults, 3.6% (95% CI, 3.0% to 4.1%) qualified for a diagnosis of severe refractory asthma, representing 10.4 patients per 10,000 inhabitants.
  
  
  CONCLUSIONS
  The prevalence of severe refractory asthma might be lower than estimated by expert opinion. This implies that currently recognized severe asthma subphenotypes could meet the criteria of rare diseases.
authors.affiliation: Department of Respiratory Medicine, Academic Medical Centre, University of Amsterdam, Amsterdam, The Netherlands. Electronic address: p.w.hekking@amc.nl.
authors.forename: Pieter-Paul W
authors.initials: PW
authors.lastname: Hekking
authors.affiliation: Department of Respiratory Medicine, Academic Medical Centre, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Reinier R
authors.initials: RR
authors.lastname: Wener
authors.affiliation: Department of Respiratory Medicine, Academic Medical Centre, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Marijke
authors.initials: M
authors.lastname: Amelink
authors.affiliation: Department of Clinical Epidemiology, Biostatistics and Bioinformatics, Academic Medical Centre, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Aelko H
authors.initials: AH
authors.lastname: Zwinderman
authors.affiliation: SIR Institute for Pharmacy Practice and Policy, Leiden, The Netherlands.
authors.forename: Marcel L
authors.initials: ML
authors.lastname: Bouvy
authors.affiliation: Department of Respiratory Medicine, Academic Medical Centre, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Elisabeth H
authors.initials: EH
authors.lastname: Bel
mesh_terms: D000280:Administration, Inhalation; D000368:Aged; D018927:Anti-Asthmatic Agents / Q000008:administration & dosage / Q000627:therapeutic use; D001249:Asthma / Q000175:diagnosis / Q000188:drug therapy / Q000453:epidemiology*; D005260:Female; D006801:Humans; D008297:Male; D055118:Medication Adherence; D008875:Middle Aged; D009426:Netherlands / Q000453:epidemiology; D015995:Prevalence; D012307:Risk Factors; D012720:Severity of Illness Index
chemical_list: D018927:Anti-Asthmatic Agents
keywords: Asthma; difficult-to-control asthma; prevalence; severe asthma; severe refractory asthma