Airway hyperresponsiveness to mannitol and methacholine and exhaled nitric oxide: a random-sample population study

Area of Science:

• Pulmonary Medicine
• Allergy and Immunology
• Diagnostic Testing

Background:

• Airway hyperresponsiveness (AHR) is a hallmark of asthma.
• Mannitol AHR has shown higher specificity than methacholine AHR in selected patient groups.
• Mannitol AHR is associated with airway inflammation markers in asthma.

Purpose of the Study:

• To compare AHR to mannitol and methacholine in a nonselected population sample.
• To assess the association of AHR to mannitol and methacholine with exhaled nitric oxide (eNO) levels.
• To evaluate the diagnostic utility of mannitol and methacholine AHR for asthma in the general population.

Main Methods:

• A study of 238 young adults randomly selected from Denmark's national civil registration list.
• Determination of AHR to mannitol and methacholine.
• Measurement of exhaled nitric oxide (eNO) levels.
• Analysis of the association between AHR, eNO, and asthma diagnosis.

Main Results:

• Mannitol AHR demonstrated higher specificity (98.4%) than methacholine AHR (80.2%) for asthma diagnosis in this population.
• Mannitol AHR had a higher positive predictive value (90.4%) compared to methacholine AHR (48.6%).
• In asthmatic subjects, mannitol AHR was significantly associated with increased eNO levels (median 47 ppb vs. 19 ppb, P=.001), unlike methacholine AHR (median 37 ppb vs. 24 ppb, P=.13).

Conclusions:

• In a general population sample, AHR to mannitol is less sensitive but more specific for asthma diagnosis than methacholine.
• AHR to mannitol is more strongly associated with ongoing airway inflammation, as evidenced by higher eNO levels.
• Mannitol AHR may be a more valuable tool for diagnosing asthma and assessing airway inflammation in the general population.