USING QUALITY-CONTROL ANALYSIS OF PEAK EXPIRATORY FLOW RECORDINGS TO GUIDE THERAPY FOR ASTHMA

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.