FEV1

[Sal678]

Is an FEV1 reading below 80 always COPD or can it be asthma ? Thanks.

[Hidden]

With the caveat that I’m not medically qualified. No, it’s not always COPD, because a person’s fev1 value has no bearing on what the underlying diagnosis is, nor is it used to make one. All an fev1 under 80% tells you is that someone has a lower than expected ability to exhale for their age, sex, and height. That’s it. It doesn’t tell you anything about the why, and it’s also completely possible to have COPD with an fev1 above 80%.

The only way to determine whether someone has asthma versus another condition using spirometry is using the value called the fev1/fvc ratio. The person does a series of blows, and if their ratio comes back lower than expected, they do a second set after having been given a bronchodilator. This process of testing after an inhaler or neb is called bronchodilator reversibility testing (BDR), and my understanding is that BDR should be done as standard in anyone that gets an fev1/fvc ratio indicating obstruction i.e. lower than normal, on their first set of blows. In the UK, this is usually classed as a ratio below 70% predicted. If after the medication the ratio increases above 70%, and either of the volumes in litres for fev1 or fvc increase by a relative 12% or more (meaning the values go up by 12% of the existing number, rather than an extra 12% on top), this indicates that someone has a reversible obstruction. Reversible obstruction demonstrates someone has asthma, because COPD and most other obstructive conditions are defined as being non-reversible: you may still see some improvement with the figures after a bronchodilator, which is why people with COPD and other conditions do use relief inhalers, but not enough to meet the 12% threshold, and the ratio would remain low. The exception to that would be someone with asthma and copd overlap syndrome (ACOS). My understanding is that for them you would expect to see the 12% relative increase in fev1 and/or fvc, but a still lower than normal ratio. However, whilst COPD is the most common cause of non-reversible obstruction, that doesn’t mean someone whose spirometry doesn’t reverse with BDR definitely has COPD. All it really tells you is that they don’t have asthma.

Does that make sense/help?

[Sal678 in reply to Hidden]

Thank you ! It was just the education that I needed to help me understand . I really appreciate the time spent writing it. 👍

[Hidden in reply to Sal678]

You’re welcome 🙂 Glad it helped.

[tonymarl]

My fev1 is 27. I suffer with emphysema. Yours could be asthma. I'd get it checked.

[soulsaver]

The trouble with these measures is that people report them differently and different countries commonly abbreviate them differently. So Fev1 is the amount of air you can forcibly blow out (ie Forced Expiry Volume) in 1 second. Volume. It's measured in litres - it's NOT a percentage.

So, to be sure, do you mean Fev1/FVC ratio which IS the 80 % to which you refer?

Or do you mean the Fev1 is 80% of expected/predicted/normal Fev1 for a given height age and gender?