title: Comparative cutoff points for adenosine monophosphate and methacholine challenge testing.
abstract: BACKGROUND
  Current use of the PC20 (provocation concentration that causes a decrease in forced expiratory volume in 1 second of 20%) cutoff point for bronchial challenge precludes its use in patients with more severe airflow obstruction.
  
  
  OBJECTIVE
  To evaluate the efficacy and safety of lower cutoff points for adenosine monophosphate (AMP) and methacholine (MCH) bronchial challenge tools to monitor response to treatment in chronic asthma.
  
  
  METHODS
  We retrospectively examined data from 5 previously published studies (2 using AMP, 2 using MCH, and 1 with MCH and AMP arms) and recalculated 10% and 15% cutoff points for AMP and MCH. Data were analyzed for correlation of single results and doubling dose shifts after anti-inflammatory treatment intervention.
  
  
  RESULTS
  A total of 175 individual MCH challenges and 152 AMP challenges were evaluated. Evaluating the doubling dose shift produced by the addition of anti-inflammatory treatment (inhaled corticosteroids or montelukast) produced the following Pearson correlation coefficients: MCH PD20 (provocation dose that causes a decrease in forced expiratory volume in 1 second of 20%) vs PD15, 0.80; MCH PD20 vs PD10, 0.65; AMP PC20 vs PC15, 0.96; and AMP PC20 vs PC10, 0.84 (P < .001 for all). Subgroup analysis of AMP for before and after inhaled corticosteroids only (n = 41) shows AMP PC20 vs PC15 of 0.92 and AMP PC20 vs PC10 of 0.84 (P < .001 for both).
  
  
  CONCLUSIONS
  The 10% and 15% cutoff points strongly predict the 20% cutoff value for AMP and MCH, as do the doubling dose shifts after anti-inflammatory treatment. The lower thresholds are suitable for monitoring response to therapy, and they expose patients to significantly less provocation agent.
authors.affiliation: Asthma and Allergy Research Group, Department of Clinical Pharmacology, Ninewells Hospital and Medical School, University of Dundee, Dundee, Scotland.
authors.forename: Tom C
authors.initials: TC
authors.lastname: Fardon
authors.forename: Emma J
authors.initials: EJ
authors.lastname: Fardon
authors.forename: Melissa R
authors.initials: MR
authors.lastname: Hodge
authors.forename: Brian J
authors.initials: BJ
authors.lastname: Lipworth
mesh_terms: D000085:Acetates / Q000008:administration & dosage / Q000627:therapeutic use; D000249:Adenosine Monophosphate / Q000008:administration & dosage; D000280:Administration, Inhalation; D000305:Adrenal Cortex Hormones / Q000008:administration & dosage / Q000627:therapeutic use; D018927:Anti-Asthmatic Agents / Q000008:administration & dosage / Q000627:therapeutic use; D001249:Asthma / Q000188:drug therapy; D016535:Bronchial Hyperreactivity / Q000188:drug therapy; D001985:Bronchial Provocation Tests / Q000379:methods / Q000592:standards*; D016085:Bronchoconstrictor Agents / Q000008:administration & dosage; D003521:Cyclopropanes; D005541:Forced Expiratory Volume; D006801:Humans; D016210:Methacholine Chloride / Q000008:administration & dosage; D011804:Quinolines / Q000008:administration & dosage / Q000627:therapeutic use; D012189:Retrospective Studies; D013440:Sulfides
chemical_list: D000085:Acetates; D000305:Adrenal Cortex Hormones; D018927:Anti-Asthmatic Agents; D016085:Bronchoconstrictor Agents; D003521:Cyclopropanes; D011804:Quinolines; D013440:Sulfides; D016210:Methacholine Chloride; D000249:Adenosine Monophosphate; C093875:montelukast