Abstract
Airway hyperresponsiveness (AHR) is defined as an excessive response to an aerosolized drug provocation that elicits little or no response in a normal person. The methacholine (MCH) challenge is a method of assessing AHR, which is one of the features that contributes to the diagnosis of asthma. However, MCH challenge has some handicaps: high economic costs, a complex process of preparation, a limited availability of the drug and a long evaluation time with a qualified technician.
The aim of this study was to identify the predictive factors of a positive MCH challenge based on the data from a baseline respiratory function test.
Between 2011 and 2015, a total of 447 patients underwent MCH challenge test (equipment: Masterscreen VIASYS with APS) after performing a baseline respiratory function test (according to the criteria of the ATS 1999). The test was considered positive when the result of the PD20 was between < 0,1 µmol and 7.8 µmol. The statistic significance was evaluated with the T-test.
A positive MCH challenge, based on ATS FEV1 criteria, was observed in 252 subjects (56,4%). A positive MCH challenge correlated statistically with age (p=0,000), FEV1% (p=0,001), FEF50% (p=0,001), RV% (p=0,049) and airway resistance Raw (p=0,005). On the other side, lung inflation and specific conductance sGaw had no correlation with the MCH challenge.
The predictive factors of a positive response to a MCH challenge are extremely important, since they may be the base of future guidelines to identify the patients that will benefit from this test. This will allow a rationale use of a complex and expensive resource with an improvement in the healthcare efficiency.
- Copyright ©ERS 2015
