Inhaled mannitol identifies methacholine-responsive children with active asthma
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Inhaled mannitol has been developed for bronchial challenge testing in adults. This study determined if mannitol could identify children with active asthma and responsive to methacholine, and whether mannitol challenge was faster to complete than methacholine challenge. Twenty-five children (aged 6-13 years) responsive to methacholine and 10 nonasthmatic children unresponsive to methacholine were studied. The methacholine challenge (Cockcroft protocol) was followed by a mannitol challenge on separate days. Twenty-one asthmatic children were positive to mannitol. Three taking inhaled corticosteroids with borderline methacholine responsiveness did not respond to mannitol, and one could not complete the mannitol challenge due to cough. The geometric mean (GM) and 95% confidence interval (CI) for PD(15) for mannitol was 39 mg (19, 78), and PC(20) for methacholine was 0.6 mg/mL (0.35-1.02) (r(p) = 0.75, p < 0.001, n = 21). Responses to mannitol were repeatable: GM PD(15) for the first challenge was 29 mg (CI: 17,50), and for the second challenge, 33 mg (CI: 20, 55) (P = 0.44, n = 9). Mannitol was faster to administer than methacholine (median (range)) 14 min (5-32) vs. 29 min (19-49), respectively (P < 0.001). Time to recover to baseline FEV(1) spontaneously and after bronchodilator administration was similar for both challenges. There were no significant falls in arterial oxygen saturations. During mannitol challenge, the mean (SD) fall in FEV(1) in nonasthmatic children was 3.1% (2.9). We conclude that mannitol identifies children with airway hyperresponsiveness and is faster to perform than the methacholine challenge.
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