Biopsy

[Kquad]

I went and had a biopsy. I mentioned to the dermatologist, I had been gluten free since march. I said I heard that could give a false negative. He said that was wrong. Also, he seemed to take the 2 biopsies from directly on a lesion. I know have the results back. One was negative. The other could not be read. Should I really take this as a true negative.

[photobuff5959]

  On 10/14/2011 at 6:45 PM, Kquad said:

I went and had a biopsy. I mentioned to the dermatologist, I had been gluten free since march. I said I heard that could give a false negative. He said that was wrong. Also, he seemed to take the 2 biopsies from directly on a lesion. I know have the results back. One was negative. The other could not be read. Should I really take this as a true negative.

I'm new to this diagnosis, but my dermatologist knew that the biopsy had to be taken from skin that had not erupted. They have to do an immunofluorescence biopsy. There are other posts in this forum about dermatolgists who understand this and those who don't. I would get a second opinion.

[itchy]

My dermatologist consultant in England said emphatically that no test would work unless I maintained a high gluten diet for a couple of weeks before testing. (Why would anyone put themselves through that misery).

Based on previous comments here, that seems to be the experience.

I would find another dermatologist.

[Kquad]

sent links with info about gluten free diet having false negatives and proper biopsy technique. He emailed me back and offered a trial dapsone. Stuff sounds scary a bit. Rash is a bit lighter this week after months. I know it can vary and has, but I may hold off a week. Feel good having a MD reconsider.

[pricklypear1971]

A DH biopsy would not depend on currently eating gluten, just having the DH rash.

An ENDOSCOPY would depend on currently (for 3 months) eating gluten.

DH biopsies have a 37% negative rate. It is a very difficult biopsy, even if it should be positive. It is unknown why it is so highly negative - they say the iga is delicate and it's hard to get a good sample - aside from the rarity of DH (or perhaps that's why it's "rare"?).

[Kquad]

  On 10/18/2011 at 4:53 AM, pricklypear1971 said:

A DH biopsy would not depend on currently eating gluten, just having the DH rash.

An ENDOSCOPY would depend on currently (for 3 months) eating gluten.

DH biopsies have a 37% negative rate. It is a very difficult biopsy, even if it should be positive. It is unknown why it is so highly negative - they say the iga is delicate and it's hard to get a good sample - aside from the rarity of DH (or perhaps that's why it's "rare"?).

I am confused, are you saying being gluten free can not give you a false negative on a DH biopsy? I swear I read that in multiple places.

[pricklypear1971]

Well, if going gluten-free gets rid of your rash then yes. However, many people with DH take months if not years to get rid of the rash on a gluten-free diet....

So, as far as I know as long as you have a rash you can have it biopsied. Some rashes are better candidates....but technically it can still be biopsied.

The rash happens where iga is stored in your skin. It can take a while for the iga to dissipate.

ENDOSCOPIES of the small intestine are supposed to be performed while eating gluten.

[Kquad]

Pricklypear,

I checked lots of websites again, many state the skin biopsy must be done while on gluten ( maybe another grey area in this disease). However, i have been on dapsone 2 days, seems to be really helping. They seem smaller and have taken on a purple tint in many areas. The improvement is not uniform and is most noted on the back

[pricklypear1971]

I'd really like to see those links. Could you post them?

[Kquad]

Open Original Shared Link

IgA antibodies must be present in the skin biopsy for a definite diagnosis (4). It is important the person continues to eat gluten as the gluten-free diet can cause false negative results.

Open Original Shared Link

Diagnosis is confirmed by a simple blood test for IgA antibodies,[17] and by a skin biopsy in which the pattern of IgA deposits in the dermal papillae, revealed by direct immunofluorescence, distinguishes it from linear IgA bullous dermatosis[8] and other forms of dermatitis. These tests should be done before the patient starts on a gluten-free diet, otherwise they might produce false negatives. If the patient has already started a gluten-free diet (there is a strong relationship with DH and coeliac sprue), it might be necessary for them to come off it for some weeks before the tests can be done reliably.

[edit]

There were more, but it is midnight.

Goodnight

[pricklypear1971]

Interesting. While I won't argue that a steady supply of iga antibodies would probably be a good thing for a biopsy, the authors seem to be missing the point that iga must still be present to cause the rash.

Iga evidently dissipates quickly for some, slowly for others.... If you still have a rash I'd guess there's plenty of iga.

I wonder if DH dx in the UK has a higher positive rate than in the US, if the guidelines are followed?

I wouldn't necessarily blame your negative/ inconclusive results on a gluten-free diet. Didn't the doc take the biopsies on top of lesions?