Comparison of four different measures of bronchial responsiveness in asthmatic children

Although several tests are available to assess the presence and severity of bronchial hyperresponsiveness (BHR), there is no agreement on the most appropriate stimulus. The most commonly used stimuli are methacholine, histamine, and exercise. Daily peak expiratory flow (PEF) variation has been reported to correlate with the severity of BHR, and in recent years this has been widely used because of its noninvasiveness and ease of performance. This study was carried out to determine the relationship among these four commonly used measures of bronchial responsiveness in asthmatic children. For this purpose, 12 asthmatic children of varying disease severity were recruited. Subjects underwent three challenges on 3 separate days in 1 week. During the week preceding the challenges (methacholine, histamine, and exercise), patients recorded PEF three times a day. All patients had PC20 less than 8 mg/ml with methacholine and histamine. Patients with PC20 greater than 3.5 mg/ml for both methacholine or histamine had negative exercise challenges. The strongest correlation was between histamine and methacholine (r = 0.95). Exercise-induced bronchospasm had substantial and significant correlation with the other three measures. No significant correlation was observed between PEF variability and histamine or methacholine. The varying degrees of relationships among the four commonly used measures suggests that each method yields information on different but related phenomena. More than one measure may be required to detect the different aspects of asthmatic bronchial responsiveness.