Diagnostic properties of inhaled mannitol in the diagnosis of asthma: a population study.

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 beta(2)-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.