Can a methacholine test be a false negative?

Your question:  Can a methacholine test be a false negative?

I have been tested for asthma, but my results came back negative. My doctor has ruled out all other possible conditions that could be a cause for my symptoms. I have all the symptoms for asthma, but they are mild. Is it possible I got a false negative because my asthma is not that severe? I did not have the 20% drop on the test, but my symptoms were present by the last vial. Confused and worried, please help!

My humble answer:  There really is no difinitive test to diagnose asthma.  However, the methacholine challenge is a pretty significant indicator.  If you have a negative methacholine challenge chances are you don’t have asthma.  The reason I can say this is because if you have asthma the challenge will make you short of breath, and a bronchodilator breathing treatment will make you feel better.  If none of these happen, chances are you don’t have asthma.  A second opinion is always a good idea, however.