Pg. Gibson et al., USING QUALITY-CONTROL ANALYSIS OF PEAK EXPIRATORY FLOW RECORDINGS TO GUIDE THERAPY FOR ASTHMA, Annals of internal medicine, 123(7), 1995, pp. 488
Objective: To compare the action points in published asthma management
plans with those derived from quality-control analysis of peak expira
tory flow recordings. Design: Longitudinal observational study. Settin
g: An ambulatory asthma education and management program in a tertiary
care hospital. Patients: 35 adults with asthma and exacerbation of as
thma. Measurements: Peak expiratory flow diaries and symptom recording
s. Results: Asthma action points from published asthma management guid
elines had poor operating characteristics. The success rate was 35% wh
en the action point was a peak expiratory flow rate less than 60% of t
he patient's best peak flow. The success rate improved to 88% when the
action point was a peak expiratory flow rate less than 80% of the pat
ient's best peak flow. Published action points had a high failure rate
. Peak flow decreased to below the published action points during a st
able period of asthma in 7% to 51% of patients studied. Action points
defined using quality-control analysis did significantly better. A pea
k flow value less than 3 standard deviations below the patient's mean
peak flow detected 84% of exacerbations and had a low failure rate (19
%). Other quality-control tests had sensitivities of 91% and 71%. Qual
ity-control action points could detect exacerbations up to 4.5 days ea
rlier than conventional methods. Conclusions: Individualized action po
ints can be derived for patients with asthma by applying quality-contr
ol analysis to peak flow recordings. These action points are more sens
itive in detecting exacerbations of asthma and have fewer false-positi
ve results. Action plans developed in this manner should be more usefu
l for the early detection of deteriorating asthma.