Diagnostic properties of inhaled mannitol in the diagnosis of asthma: A population study
Received 23 October 2008; received in revised form 19 June 2009; accepted 23 June 2009. published online 10 August 2009.
Background
A new indirect bronchial provocation test measuring airway responsiveness by using inhaled mannitol was recently introduced.
Objective
The aim of this study was to examine the diagnostic properties of airway responsiveness to inhaled mannitol in the assessment of asthma in an unselected sample of young adults.
Methods
Two hundred thirty-eight young adults randomly drawn from the nationwide civil registration list were challenged with inhaled, dry-powder mannitol. A respiratory specialist, blind to the test results, classified all 238 subjects with respect to the presence of asthma. The classification was based on respiratory symptoms, spirometric results, atopy, and fraction of exhaled nitric oxide values and response to inhaled β2-agonists. On this basis, sensitivity, specificity, and predictive values were assessed to different cutoff values of the test. A receiver operating characteristic curve was constructed, and the accuracy of the test, defined as the area under the curve, was computed.
Results
Fifty-one (21.4%) subjects had current asthma. Of 33 subjects with airway hyperresponsiveness to mannitol, 30 had current asthma. The specificity and sensitivity were 98.4% (95% CI, 96.2% to 99.4%) and 58.8% (95% CI, 50.7% to 62.6%), respectively. The positive predictive value (PPV) and negative predictive value (NPV) were 90.9% (95% CI, 78.4% to 96.8%) and 89.8 (95% CI, 87.7% to 90.7%), respectively. The area under the receiver operating characteristic curve was 0.89 (95% CI, 0.83-0.95).
Conclusions
In an unselected sample of young adults, bronchial provocation with inhaled dry-powder mannitol had a high diagnostic specificity for the diagnosis of asthma.
Department of Respiratory Medicine L, Bispebjerg University Hospital, Copenhagen, Denmark
Reprint requests: Asger Sverrild, BMedSc, Department of Respiratory Medicine L, Bispebjerg Hospital, DK-2400 Copenhagen NV, Denmark.
The Danish Agency for Science, Technology and Innovation, an institution under the Danish Ministry of Science, Technology and Innovation, granted a 1-year scholarship. Pharmaxis provided the research team with an unrestricted grant, with which one of the research assistants was employed. Moreover, parts of the Mannitol kits were delivered at no cost by Pharmaxis.
Disclosure of potential conflict of interest: V. Backer has received research support from Pharmaxis. The rest of the authors have declared that they have no conflict of interest.
ABSTRACT