Positive PCR, but Toxins A and B not detected?

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STS-0
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Positive PCR, but Toxins A and B not detected?

Postby STS-0 » Mon Apr 10, 2017 2:48 pm

What is the significance of having a positive PCR, but no toxin A or B detected? Mine has always been this way.

Musings
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Re: Positive PCR, but Toxins A and B not detected?

Postby Musings » Mon Apr 10, 2017 3:53 pm

Did they do a follow up test after the PCR? Usually, if the PCR is negative they will do a DNA Amplification test which looks for the toxins as well as the antigen which is where the results will state toxins not detected. Generally speaking, from my understanding, being positive for the antigen but negative for toxins means either the toxin levels were too low for detection and usually mean a colonization versus active infection.

You can read more about it here (http://labmed.yale.edu/virology/Newslet ... _284_5.pdf)

I tested positive for the antigen, but negative for toxins, and if am not having active symptoms have decided to not treat as I believe I over-treated in the past.

For most relapses, you should be treating on symptoms, not test results.

~Lauren

AnxiousJ
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Re: Positive PCR, but Toxins A and B not detected?

Postby AnxiousJ » Mon Apr 10, 2017 4:30 pm

I thought that if you test positive for antigen but neg for toxins that means that you had the infection at some point in your lifetime. Last year I tested positive for antigen and negative for toxins and then had a neg PCR. Aren't they two different tests? Now, I am confused.

roy
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Re: Positive PCR, but Toxins A and B not detected?

Postby roy » Mon Apr 10, 2017 4:48 pm

There's 3 types of test
Antigen: detects the chemical released by all types of c.diff even the harmless strains.
PCR : that ones now the most commonly used one.
It amplifies the minute DNA that c.diff gives off when it produces toxin B it does not detect toxin A.
The problem with this test is that it is very sensative and picks up the slightest infection even if your not sick.
Both of the above tests can be followed with an EIA test that only looks for the toxins.
If either of the first two types of tests are positive and your symptoms do not indicate an active infection its a good Dr that orders an EIA test to confirm if there are toxins in your stool.
If there's no toxin and you don't have typical D then the diagnosis is you might be colonised but DO NOT need treating!

AnxiousJ
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Re: Positive PCR, but Toxins A and B not detected?

Postby AnxiousJ » Mon Apr 10, 2017 4:55 pm

So there is no way to know if you are colonized?

roy
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Re: Positive PCR, but Toxins A and B not detected?

Postby roy » Mon Apr 10, 2017 5:14 pm

Antigen and PCR will both detect if your colonised.
Guidlines say that colonisation without D should never be treated, treating can cause it to go full blown.
Remember though that up to 5% of healthy people are colonised, a 2 week stay in hospital increases that to 17% and for those in a care facility it can rise to 50%
C.diff is a normal gut flora and only becomes a disease if it overgrows because of damage done to the other gut flora.
In fact being colonised by a lesser c.diff strain that's not causing disease might even give a degree of immunisation type protection against the nasty strains!

AnxiousJ
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Re: Positive PCR, but Toxins A and B not detected?

Postby AnxiousJ » Mon Apr 10, 2017 5:24 pm

Thank you. So if I tested last year as GDH pos, toxin and EIA neg does that mean I am colonized or not colonied? Can that GDH status change? For instance, can you be GDH pos and eventually become GDH neg or does it typically stay pos?

roy
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Re: Positive PCR, but Toxins A and B not detected?

Postby roy » Mon Apr 10, 2017 5:37 pm

Yes it can change.
The 5% who are positive could be a different 5% a year later.
But unless you have D you should not test and labs should also protect you by refusing to test formed stool.

AnxiousJ
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Re: Positive PCR, but Toxins A and B not detected?

Postby AnxiousJ » Mon Apr 10, 2017 5:43 pm

Thank you! Yes, I have tested 4 times since April but that is bc I have IBS now and wasn't sure what was going on. Thank you...this is good information.

STS-0
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Re: Positive PCR, but Toxins A and B not detected?

Postby STS-0 » Mon Apr 10, 2017 9:27 pm

I don't understand. Every single time I've been symptomatic, my tests have been PCR positive, A and B toxin not detected. During Vanco I get much, much better, but then I relapse afterward and always get the same results: PCR positive 'Toxigenic C. Diff detected', toxin A and B not detected.

How can I have toxigenic C. Diff without A and B toxins detected? And why am I having symptoms if the C. Diff are not secreting toxins?

amyc
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Re: Positive PCR, but Toxins A and B not detected?

Postby amyc » Tue Apr 11, 2017 12:04 am

We had a lady who went to see Dr Colleen Kelly in RI, and Dr Kelly told her the tests weren't worth much, and she treats based on symptoms mostly, as I recall. The toxin test used to be considered really unreliable, and I remember people would have to test multiple times to get a positive toxin test. That's why they developed the PCR test. PCR tests for the DNA for toxin B, so if it is positive, that means you have the DNA for toxin B in your stool.

Short answer--symptoms? I'd treat, but that's just me.

beth22
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Re: Positive PCR, but Toxins A and B not detected?

Postby beth22 » Tue Apr 11, 2017 2:02 am

I had the same thing happen last year. I had taken antibiotics when in the hospital and about 6 weeks later had a day or two of D. I tested positive on the PCR, but by then the D had subsided. I tested a month later, still positive. Tested again, still positive. A few months later, the hospital started sending positive PCR tests to be done by EIA because they found that they were treating people who did not need to be treated. Basically, I am colonized, but I do not have the symptoms. The EIA test was negative and they considered the entire test negative.

I have not tested in many months now, but I assume the PCR would still be positive. My doctors told me under no circumstances to treat that without having D symptoms. The EIA tests have been improved since years ago when they were not very reliable.

georgina
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Re: Positive PCR, but Toxins A and B not detected?

Postby georgina » Tue Apr 11, 2017 2:38 am

Test for Toxin A/B are considered to be 70% accurate , PCR however is a DNA test that has over 90% accuracy and if PCR is positive then clearly you are a Cdiff carrier but if symptoms are not present the treatment is not required . Cdiff should be treated based on symptoms along with a positive test not only based on test results.
I'm still testing positive for toxins but I decided not to treat as my symptoms are mild and intermitent, I'm trying to let my own immune system take care of the infection.Of course , if things go full blown again , I will jump back on meds.

STS-0
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Re: Positive PCR, but Toxins A and B not detected?

Postby STS-0 » Tue Apr 11, 2017 7:33 am

That still doesn't explain how I can be PCR positive 'toxigenic C. Diff detected,' and A/B toxin not detected while I'm symptomatic? How can I have toxigenic C. Diff without the toxins? And why am I symptomatic without A and B toxins present, when the toxins are what cause C. Diff symptoms in the first place?

roy
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Re: Positive PCR, but Toxins A and B not detected?

Postby roy » Tue Apr 11, 2017 8:18 am

What are your symptoms when you relapse?
PCR detects the slightest amount of toxin, that's where the amplification part comes in!


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