Early detection of asthma exacerbations and the use of action points for treatment decisions in self-management plans

Background: Written asthma action plans specify the level of symptoms or peak expiratory flow (PEF) (action points) at which to increase medication in order to prevent or reduce severity of exacerbations. Few currently used action points are validated. Our aim was to develop optimal action points for early detection of asthma exacerbations. Methods: We analyzed daily morning PEF and symptoms from two studies. The development dataset consisted of 165 patients and 88 exacerbations (Taylor, Thorax 1998). Every week was coded “stable week” or “pre-exacerbation week”. Potential action points were based on Quality Control Analysis of PEF or symptoms, or percentage personal best. Sensitivity and specificity for predicting an exacerbation and the number of days the exacerbation was diagnosed earlier were calculated. Optimal action points were based on these parameters. Their performance was compared to the published NAEPP action point in the validation dataset, consisting of 94 patients and 20 exacerbations (Smith, NEJM 2005). Results: The main differences between action points were in false positive rate and early detection (Table 1). Combination of PEF+symptoms action points performed best, due to improved specificity and early detection. Table 1 Action Points Early detection (d) Sens (%) Spec (%) Development Symp 2.9 88.5 86.3 PEF 2.9 90.8 93.9 Symp + PEF same day 1.4 80.5 98.3 Symp + PEF 1 week 4.1 85.1 97.2 Validation Symp 3.3 75.0 86.2 PEF 4.2 100 92.5 Symp + PEF same day 1.7 75.0 98.3 Symp + PEF 1 week 5.1 75.0 97.4 NAEPP 4.9 100 86.8 Conclusion: Early detection of asthma exacerbations can be improved by combining symptoms and peak flow measurements over one week in a single action point.