Allergy testing and Spiro ....?

After seeing the nurse/GP yesterday they have decided to get allergy testing done on me as I am allergic to something but i don't know what - what does this involve?

They also want to do some sort of test they said spiro something to check the lungs - am not too sure what it is though . - does anyone know and what does it involve? it sounds scary.

arghhh!

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Hi Laurenjayne,

Allergy testing can take several forms. There is a simple blood test, the RAST test, which looks at the specific levels of the main allergy-causing antibody, IgE, for each common potential allergen. It is fairly accurate, although it is possible to be allergic to something and not to have a positive RAST - sometimes other antibodies other than IgE can be involved.

There are also skin prick tests, which involve making a series of tiny scratches on the skin using sterile needles dipped in a concentrated form of each potential allergen - after half an hour or so, a red wheal will form on the skin in response to these allergens, and measuring this gives some idea (although some say not a particularly accurate idea) of the severity of the allergic response. This test sounds worse than it is - the needles they use are very very fine, and it shouldn't hurt - the worst thing usually is that the site can be a bit itchy if you have a positive reaction. You would probably be asked to stop any antihistamines before the test.

Another form of allergy testing, not very often used now, is the exclusion diet, where the diet is reduced to a very plain and basic one (sometimes even just protein drinks) for a few days and then individual foods are introduced, one each day, to see if there is any reaction to a specific one. As I say, this is not often done now, as it is logistically difficult and it is thought that other methods provide results which are as valid.

The 'spiro something' sounds like spirometry, which is one of the most basic forms of lung function testing. It is used both to confirm a diagnosis of asthma and to measure how severely it is affecting you at the moment. Basically all you will be asked to do is to put some nose clips on and breath out as hard as you can for as long as you can into a flexible tube attached to a machine. You will probably be asked to do this several times - at least three, but more if they are not happy with your technique the first few times - it does take practice! It is not painful, although it can be tiring, and some people find that it does provoke a bit of bronchospasm or wheeze, so be sure to take your inhaler with you. They may ask you not to take inhalers or certain other medications for a few hours before doing the test, to ensure that the results are as accurate as possible - however, don't stop anything unless they ask you to and you have checked with your doctor that it is safe to do so! If they find an abnormality on your spirometry, they may ask you to use an inhaler or nebuliser and then repeat the testing in a few minutes time, which is a form of diagnostic test and a pretty good confirmation of asthma.

The main measurements they will get from the spirometry are: Peak Expiratory Flow Rate (PEFR) a.k.a. the good old peak flow, which is a pretty good measure of how hard and fast you can blow out, which reflects how narrowed the tubes are; the Forced Expiratory Volume in 1 second (FEV1), which is also a measure of how hard and fast you can blow out and therefore how narrow the tubes are, but can be a little more accurate and sensitive than the PEFR; and the Forced Vital Capacity (FVC), which is a measure of the total amount of air which you can breath out when emptying your lungs completely - this is usually normal in asthma, but can be used to pick out other respiratory illnesses that might be masquerading as asthma (unlikely in most people).

You can expect to be weighed and measured so that they can accurately calculate what your predicted values for these figures should be. You will then be given the absolute value and the percentage of the predicated value for each parameter. They will usually take the best reading of at least three. They will usually give you a copy of your results if you ask, which I find useful for my own personal records.

One thing that it is important to say is that normal spirometry does not rule out a diagnosis of asthma - in fact, as asthma is characteristically a condition of *reversible* air-flow obstruction, normal spirometry at times is to be expected. It is also important to point out that bad spirometry does not necessarily imply that you have severe asthma or that there is any sort of permanent damage to your lungs, just that you are having a bad day or there is room for improvement in your asthma control. It can be alarming to see a figure of 50 - 60% of predicted appear on the computer screen, but that is not the same as saying that your lungs are functioning at 50 - 60% of their capacity. Also, some people occasionally just cannot ever reach their predicted value - not because of illness or uncontrolled asthma, but just because of individual variability - the result will still be quite normal for them. The predicted values are based on studies of the population as a whole, and there are always some totally normal people who will fall outside of the usual limits.

I guess the key point is that spirometry results can be confusing and frightening to try and interpret (I certainly find them so, even as a medic!) but that they should not be considered in isolation but in combination with your symptoms, past history, medication and so on. If you do have concerns about the results, do discuss them with your GP - I am sure he/she will be following you up, in any case.

All the best, and let us know how it goes

Em H

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Thank you EmH for the long and detailed reply - it was very much appreciated and i feel i understand it all a lot more now. thank you

lauren xx

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No problem, Laurenjayne, do feel free to post or message me if you have any more questions or worries.

I have edited my previous post slightly as I had given the wrong name for one of the measures of spirometry, sorry about that, but the essence of it remains the same!

Em