Today I have suddenly been asked to see the nurse for a FeNO test. This makes me anxious. I gather they measure eosinophilic inflammation, but I appear to be low on that. I also gather that type of inflammation is mainly linked with allergies, and it is not allergies that causes my asthma symptoms. Environmental factors like indoor air pollution and cold air is much more of a thing for me. I have been remarkably well for some time now, which is great, but I have had some significantly bad periods in the past. Also there is family history. I thought myself I would get away with lower medication this winter, but as the cold and damp hit some triggers were immediately apparent, so I increased to my winter levels.
If someone could help me understand the relationships between the FeNO test, eosonophils, asthma, allergies and sensitivities, and notably pollution I would be grateful. I fear my medication may be reduced, leaving me much more exposed.
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Wheezycat
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I like the FeNo Test. You blow into a machine that often has a picture that you need to blow to keep it in the same place. You hold the picture for example race car on the track until the end. Then the machine gives you a score. Anything under 10 shows a low level of inflammation in your airways. I ask to do this test each time I visit my tertiary asthma centre. It helps me know myself how well controlled my asthma is on my current inhalers.
LysistrataAdministratorCommunity Ambassador• in reply to
Hi, I will post more below but the cutoffs I've seen are more like under 25 ppb (parts per billion) is 'normal', 26-49 is 'medium' and 50+ is 'high'. I've had anything from about 16 to 55 but my asthma is mostly non-eosinophilic and non-allergic (so not the kind that necessarily gets picked up by FENO). I suspect I have elements of eosinophilic though which may be why it sometimes creeps into the 'medium' range. It never really matches up with my symptoms though.
I do not know much in big words sorry. I have autism and learning difficulties. I just enjoy doing the test with the various graphics. The first time I met the FeNo test it was a silver ball you blew up and had to keep up. But it quickly changed to graphics like clouds, balloons and now racing cars. I guess for me it is more fun than the spiro. I am nearly always a 10 or below and it helps me motivate to manage my asthma well so that I can keep that score.
I’m sorry, I can’t explain it better as my understanding of it isn’t the greatest. I do know that eosinophils have to do white blood cells, which I believe increase with inflammation. The person who knows this through and through is Lysistrata.
My asthma is mainly caused by dust mites, often provoked by cold air.
I unexpectedly had a feno test administered, when my asthma was under control. I had a reading of 45, which the nurse said was the level at which they diagnosed asthma.
I am pleased to have the test, as the nurse tweaked my medicines and routines. The feno test readings, alongside my spirometry readings, will help give her an idea as to whether the changes have worked.
Hmm glad it's been helpful for you, and it does sound like they're using FENO to tweak your medication, which is really how it can be helpful for most people it works well for.
But aghh, '45 is the level at which we diagnose asthma' - I REALLY hope that doesn't mean they're using it as a single test to diagnose asthma in other people. It isn't meant to be used that way, as a yes-no test for asthma diagnosis.
They may be asking you to do FENO to see if you need more inhaled steroid – this is one way it can be used. Or it can be used as *part*of diagnosis: it is absolutely NOT meant to be used as ‘above this level you have asthma, below you don’t’. You are already on medication though so it shouldn’t be a thing re ‘proving’ asthma.
This is all simplified as it is a complex area, but hopefully helpful. Apologies in advance if you already know any of this and it seems too simple.
There are different types of inflammation in asthma, sometimes more than one at once (see below). This refers to biological processes making airways twitchy and prone to overreact. The end result is airways becoming inflamed and getting narrow.
It can be very confusing because triggers like pollution, weather/cold or hot air, smoke, infections etc seem to be common across types of asthma, and previously there were attempts to create types of asthma on the basis of triggers. This has now been replaced more or less with understanding what’s going on biologically – not all types are as well understood as others though.
It does seem like some triggers are more common to certain types though: the obvious one is things like dust mites or animals for allergic asthma. Some triggers seem to act more directly on twitchy airways rather than triggering an indirect process (or do both). Those are triggers like smoke, scents, weather changes. However, I know plenty of asthmatics find triggers can definitely play off each other and make the airways more twitchy for the next trigger.
The twitchiness of the airway in this case doesn’t have to be due to one type of asthma or another – possibly, scents and weather and smoke *might* be more of an issue for non-eosinophilic types, but I’ve met people across all types who react to some of the same triggers and present the same way in an attack. I am REALLY oversimplifying here because this is a huge topic, but hopefully this gives an idea of why triggers have a complex relationship with tests/markers like FENO.
As you asked about pollution: FENO has, guess what, a complex relationship with it! Pollution itself is made up of different components and it seems like some are more or less linked to different types of inflammation in asthma, and to FENO.
Type 2 high: **FENO measures eosinophilic and/or allergic inflammation**
These types of inflammation in asthma are related. They’re often grouped together as 'Type 2' inflammation, or T2 high, named after Type 2 helper T cells, white blood cells which play a key part of this type of inflammation. This kind of asthma is better understood currently, and it’s also easier to measure and to treat than Type 2 low asthma.
• Eosinophilic inflammation (Type 2): higher levels of eosinophils, a specific white blood cell that was mainly designed to fight parasites and is involved in some inflammatory diseases. Most of the current biologic treatments are designed to target eosinophils. You can get a good idea of how many eosinophils are in the airways by doing a blood test, though it’s not perfect. Steroids reduce eosinophil levels, but they don’t always fix the asthma because it’s complex. Newer biologic treatments like Nucala (mepolizumab), Fasenra (benralizumab) and Dupixent (dupilumab) target eosinophils.
• Allergic inflammation (also Type 2): related to eosinophilic but more specifically, to a type of antibody called IgE. People with allergic asthma and other allergic diseases produce too much IgE, because their immune systems think harmless substances are not harmless and need to be removed. All that excessive IgE then triggers mast cells to release a lot of substances like histamine, leading to asthma and/or allergy symptoms. Xolair (omalizumab) targets IgE; dupilumab also helps allergic asthma.
• Mixed eosinophilic/allergic/neutrophilic: pick and mix! Hard to deal with because you have multiple mechanisms going on to cause airway inflammation and narrowing.
Type 2 low: **FENO is not designed to detect Type 2 low inflammation in asthma**
• Neutrophilic (non-Type 2/type 2 low): this involves a type of white blood cell called a neutrophil that acts as the first line of defence in your immune system. These cells can be very aggressive and can release a lot of substances while they work which can damage the airways and cause inflammation. Neutrophilic asthma is less well understood and possibly less common, but it can be just as severe and persistent as Type 2 asthma. Typically, Type 2 low asthma doesn’t respond well to steroids (except some inhaled steroids seem to be needed in all asthma, oddly). You can’t treat it like eosinophilic asthma (ie, get rid of the eosinophils), because we need neutrophils to fight infections, even if we don’t need them to be so aggressive. It can be difficult to identify this type of asthma because neutrophil numbers in the blood don’t really tell you what they’re doing in the airways. Also, steroids (especially pred) seem to increase neutrophils in the blood.
• Paucigranulocytic (Type 2 low): asthma that as far as we know, doesn’t involve granulocytes. Granulocytes are white blood cells in the immune system which contain granules – those are basically a cocktail of toxic substances that these cells chuck at what they think are invaders, to kill them. Or to just cause havoc in your own body, in the case of asthma and other diseases. Eosinophils, neutrophils, basophils (not mentioned above but also involved in asthma, no specific treatments though) and mast cells are granulocytes. Paucigranulocytic asthma isn’t well understood, and isn’t easy to identify.
FENO
FENO appears to somewhat match up with other measures of Type 2 inflammation (like measuring blood eosinophils). The GINA guidelines (international asthma guidelines) find the evidence shows that it isn't more helpful for most people for preventing attacks than the current approach in the guidelines based on things like symptoms and peak flow. Obviously for some people, FENO may be very helpful, just like peak flow is more or less helpful for some people.
For SOME people with Type 2 inflammation, FENO still isn't that helpful. I know of at least one person on this forum with eosinophilic asthma whose FENO is out of step - it's low when they're first getting worse and goes up when they recover. If you went by FENO alone you'd say they're fine and not having an attack when they are.
Low FENO, especially on meds, doesn't mean no asthma. It can just mean that this type of inflammation (Type 2) is currently more or less under control – or as with the person above, that the inflammation ISN’T controlled but the FENO hasn’t caught up yet!
I hope this enormous essay is useful to you – obviously please say if anything isn’t making sense or I haven’t covered anything, and I’ll try to answer.
No worries - I may have gone a little over the top hehe but hopefully at least some of it is helpful and it makes sense!
For anyone after a shorter version who doesn't need/want that much, there's a great link with a video from Dr Andy which explains very well what FENO is for: healthunlocked.com/api/redi...
Thanks! I hadn’t realised. For me it is helpful to be well informed, to my edge of non comprehension, as I then function better with the condition, and remedies. So I appreciate your information enormously, both now and at many previous times.
Hi sorry jump onto the post. I found this very interesting. I'm under severe Hospital my feno is only 18 was 22 been on steroids 8months now down to 1mg. Still getting asthma attacks from tiggers there saying my asthma under control.
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