Abstract

This study showed that although mannitol BPT results were positive in the minority of subjects (30%), those with a positive mannitol BPT result had more active disease in terms of greater airflow limitation and more eosinophilic inflammation and higher exhaled nitric oxide levels compared with values seen in subjects with a negative mannitol BPT result. Therefore the mannitol BPT might be more relevant than the methacholine BPT for assessing the impairment/disability of subjects with a previous diagnosis of OA. However, the mannitol BPT was not sensitive for identification of AHR to methacholine in this population. The mannitol BPT was able to successfully induce sputum for obtaining valid sputum cell counts. The quality of sputum samples was better with hypertonic saline than with mannitol but still of good quality after using mannitol. There was a significant discrepancy between the cell counts obtained with hypertonic saline and mannitol for sputum induction. Furthermore, there was a substantial difference between the classifications in the different inflammatory phenotypes between the 2 methods, as shown by the low agreement of the eosinophil (? = 0.1) and paucigranulocytic (? = 0.1) phenotypes between the methacholine and mannitol BPTs (Table II). These results differ somewhat, with previous results showing similar eosinophil and neutrophil cell counts after hypertonic saline and mannitol.9 The protocols used to administer hypertonic saline differed significantly between the 2 studies, which might explain these differences.

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