ANCA results

[CathT]

Can someone explain ANCA to me please. I had a positive result then a negative result. The doctor yesterday in A&E has sent off for another ANCA test to be done. What is the difference in vasculitis between positive and negative.

[Ayla Volunteer]

ANCA stands for anti neutrophil cytoplasmic antibody - a very forgetable mouthful, Cath. A positive result just means that your body is producing antibodies, which are detectable in your bloodstream and an auto immune disease is indicated. Just which one depends on what sort of ANCA you have. Positive C ANCA indicates either GPA (previously called WG) or EGPA (previously CSS) and P ANCA either MPA or, possibly, EGPA. Your consultant has no doubt ordered other blood tests which will confirm which type of vasculitis you are suffering from.

There are a few other possibilities which can show a positive ANCA result but, unless you have had a kidney infection before your positive test result, vasculitis is the most likely.

Now, your negative result. I am presuming you haven't had a long gap, with significant medication therapy in between the positive and negative ANCA results? If not, then I suspect that one of the tests is inaccurate and that your consultant has ordered another blood test to check which one is the accurate result! All pretty confusing, yes?

Having said all this, the main thing to check is how you are feeling. ANCA results can be, and often are, an unreliable indicator of vasculitis activity!

Let us know how things develop, and good luck!

Ayla

[CathT in reply to Ayla]

Thanks Ayla, I was told I had GCA which quickly changed to unspecified, one because I am 46 so to young for it! I also get a rash and a constant runny nose which they confirmed was vascular. So they determined I have different vessel involvement. Both test were carried out while only on pred. I am now getting terrible pain through my right side under my ribs, which they say is vasculitis. However my markers are only slightly raised. They are also checking for lupus as I have sticky blood. Thanks again for your explanation it is a great help.

[John_Mills Volunteer]

Well Cath, I think Ayla has just about said it all. The laboratory test for ANCA is quite involved and complex and is very technique sensitive. Consequently, results vary between labs, so a lot depends on getting consecutive results from the same lab. As Ayla said, any treatment, especially with prednisolone, can suppress the ANCA result and produce a false negative. Just to add to the confusion, the ANCA test is not a reliable indicator of disease activity or a reliable predictor of disease relapse. As Ayla said, it is the symptoms & how the patient feels that is a more reliable indicator. Unfortunately, so many doctors do not realise this and their treatment planning is ruled by misleading blood tests.

Best wishes - John