title: Relationship of non-specific airway hyperresponsiveness (AHR) to measures of peak expiratory flow (PEF) variability.
abstract: BACKGROUND
  The relationship between airway hyper-responsiveness (AHR) and clinical asthma remains controversial and unclear.
  
  
  OBJECTIVE
  To test the hypothesis that serial measures of variability of peak expiratory flow rate (PEF) correlate with serial measures of AHR, and to determine which mathematical expression of variability provides the best correlation.
  
  
  METHODS
  A longitudinal study over 180 days of 20 atopic, moderately severe asthmatics was undertaken. A diary of medication use and morning and evening PEFR before and after beta agonist was kept and AHR (PD20 histamine) was measured at three-weekly intervals. Using group data (128 sets) in PD20 was correlated with various measures of PEF variability over 9 days.
  
  
  RESULTS
  [Table: see text] Within the group there was a weak but highly statistically significant correlation between AHR and measures of PEF variability--the strongest correlation being with mean morning PEF. Within individual subjects, however, the correlation was not a consistent finding and only four patients had a statistically significant relationship (p < 0.05) between AHR and mean morning PEF.
  
  
  CONCLUSIONS
  These results suggest that while PEF variability may reflect AHR for the purposes of epidemiologic studies, it is unlikely to be useful as a simple 'non-invasive' means of assessing AHR in individual patients. More complex measures of PEF variability do not have an advantage over simpler measures such as mean morning PEF.
authors.affiliation: Department of Respiratory Medicine, Green Lane Hospital, Auckland, New Zealand.
authors.forename: J
authors.initials: J
authors.lastname: Kolbe
authors.forename: G
authors.initials: G
authors.lastname: Richards
authors.forename: J
authors.initials: J
authors.lastname: Mercer-Fenwick
authors.forename: H
authors.initials: H
authors.lastname: Rea
mesh_terms: D000293:Adolescent; D000328:Adult; D001249:Asthma / Q000503:physiopathology*; D016535:Bronchial Hyperreactivity / Q000175:diagnosis*; D006801:Humans; D008875:Middle Aged; D010366:Peak Expiratory Flow Rate; D011446:Prospective Studies