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methacholine challenge

Question:

I had a methacholine challenge – I had a 15% fall in FEV1.  Different docs have said different things about this being positive or not.  Some say borderline, others say definitely negative.  I’ve read in some places that 15% is considered positive.  Anyone have a 15% change and get an asthma diagnosis?  Thanks for any info…. Ellen

Response:

I had a methacholine challenge – I had a 15% fall in FEV1.  Different docs have said different things about this being positive or not.  Some say borderline, others say definitely negative.  I’ve read in some places that 15% is considered positive.  Anyone have a 15% change and get an asthma diagnosis?  Thanks for any info…. Ellen

Hi Ellen,     This is just an opinion, but I think that to make the diagnosis of asthma or not the doctor should look at more then just the methacholine challenge results.  Other symptoms should also be included in the decision. pw.

Response:

I had a methacholine challenge – I had a 15% fall in FEV1.  Different docs have said different things about this being positive or not.  Some say borderline, others say definitely negative.  I’ve read in some places that 15% is considered positive.  Anyone have a 15% change and get an asthma diagnosis?  Thanks for any info….

The methacholine challenge test may be administered when the asthma diagnosis is in doubt. I understand up to 5 different levels of methacholine are administered; a 20% drop in lung function indicates the possibility of asthma; failure to show a 20% drop at the highest level of methacholine tends to rule out asthma. I just checked my book ‘The Asthma Sourcebook’ written by pulmonologist Francis Adams, MD. He says for the challenge test to be positive there must be a least a 15% drop in airflow after the challenge. A pulmonologist would use these results along with spirometry to help diagnose the degrees of asthma, bronchitis, & emphysema. Here are some links: http://www.ama-assn.org/sci-pubs/journals/archive/inte/vol_157/no_17/… Methacholine Inhalation Challenge Excerpt: "With respect to MICs, there were no significant differences between groups in the cumulative dose of methacholine that provoked a 20% decrease in forced expiratory volume in 1 second from the postsaline baseline value (PD20 values), slopes of dose-response curves, and maximal-response plateaus." http://www.med.umich.edu/intmed/pulmonary/pulminh.html Inhalation Challenge Test (UMich) http://www.ama-assn.org/special/asthma/treatmnt/guide/guidelin/comp1/…  EPR2  Excerpt: "Bronchoprovocation with methacholine, histamine, or exercise challenge may be useful when asthma is suspected and spirometry is normal or near normal. For safety reasons, bronchoprovocation testing should be carried out by a trained individual in an appropriate facility and is not generally recommended if the FEV1 is <65 percent predicted. A negative bronchoprovocation may be helpful to rule out asthma." Ellis

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I know there are many meds that you should not take before the methacholine challenge test.  Is Zyban (Welbutrin) one of them?  I have decided I have had enough of this nicotine habit and got my prescription today and finally a referral to an asthma specialist.  I wanted to start on the Zyban this weekend (looking at a quit date of Feb 17), but I am now scheduled for the methacholine challenge test Monday and I don’t want to screw up any results after waiting months for this referral. Mary-Ellen

Response:

I know there are many meds that you should not take before the methacholine challenge test.  Is Zyban (Welbutrin) one of them?  I have decided I have had enough of this nicotine habit and got my prescription today and finally a referral to an asthma specialist.  I wanted to start on the Zyban this weekend (looking at a quit date of Feb 17), but I am now scheduled for the methacholine challenge test Monday and I don’t want to screw up any results after waiting months for this referral. Mary-Ellen

Hmmmm. I would think you would want to quit smoking before you had the methacholine challenge test; perhaps quiting smoking would reduce or eliminate your symptoms so you don’t have to have the methacholine challenge test. It’s not a trivial test; not a lot of fun from what I hear. (I’ve had pulmonary function testing in a pulmonary test lab, but not the challenge–which is only given when the asthma diagnosis is in doubt.) I would also wonder how valid the results would be if you are still smoking–just my opinion, ask your pulmonologist. [Lung function is tested, then methacholine is administered and lung function retested, looking for a 20% drop; if 20% or more drop occurs the antidote is given (bronchodilator); if not, successively higher levels of methacholine are administed (5 levels) and test repeated. A positive test (20% drop) indicates possbility of asthma, a negative result (<20% drop) indicates you probably don’t have asthma; but more probably chronic bronchitis. In general you shouldn’t take asthma meds in the 12 hr. or so before pulmonary tests; again, check with your doctor. Regarding Zyban, there is a web site at: http://www.zyban.com/Pages/info.html Excerpt: "It takes about 1 week for ZYBAN to reach the right levels in your body  to be effective. So, to maximize your chance of quitting, you should not  stop smoking until you have been taking ZYBAN for 1 week. You should set  a date to stop smoking during the second week you’re taking ZYBAN." I doubt that Zyban would affect the challenge test, I think smoking is more likely to affect it. My advice is call your pulmonologist or the pulmonary lab giving the test and ask them. Ellis, not a doctor, not a smoker.

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