Control charts demonstrated limited utility for the monitoring of lung function in asthma

Publication Type:
Journal Article
Citation:
Journal of Clinical Epidemiology, 2012, 65 (1), pp. 53 - 61
Issue Date:
2012-01-01
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Objective: Statistical process control charts have been advocated for use in monitoring of lung function in asthma. We aimed to evaluate their application in asthma using existing data from a randomized trial. Study Design and Setting: Patients on optimal inhaled corticosteroid/bronchodilator therapy (n = 81) were randomized to continue the same or change to corticosteroid alone. Baseline statistical control was assessed from 20 days of electronically recorded lung function (peak expiratory flow [PEF], forced expiratory volume in one second [FEV1]). The ability to detect lung function changes was assessed during 10 days after randomization. Results: PEF measurements were in statistical control during baseline for only 59-79% of patients for different combinations of five control chart rules (e.g., Rule 1: >3 standard deviations outside mean and 95% expected to be in control), with similar proportions for FEV1. After randomization, among those previously in statistical control, Rule 1 signaled lower FEV1for 35% of patients randomized to treatment change compared with 6% continuing baseline treatment (P = 0.004). Control charts performed poorly for PEF, signaling a decrease for 8% of patients randomized to treatment change compared with 11% continuing treatment (P = 0.7). A paradoxical increase was signaled for many patients continuing treatment. Conclusion: Control charts may not be suitable for use in many patients with asthma. © 2012 Elsevier Inc. All rights reserved.
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