How common is a false negative result?

Please limit your post to questions only. You can ask multiple questions in the post. (One post per person per day about yourself. See exception in General C. diff.Discussion.)
poppy86
Regular Contributor
Posts: 197
Joined: Sun Mar 29, 2020 10:23 pm

How common is a false negative result?

Postby poppy86 » Sun May 17, 2020 11:09 am

I'm at the end of my vanco taper, taking 1 pill a day (supposed to be every other day, but I was told to stick to 1 per day right now). For the past 4 days I've been having frequent D, and blood and mucus. I brought in a stool sample, and today it tested negative for cdiff toxin. But I have the same exact symptoms as when I was first diagnosed, so I thought this was a relapse.

Is it possible it's a false negative? I feel so sick, I don't know what's happening to me. I'm waiting for a call back from the on-call doctor.

poppy86
Regular Contributor
Posts: 197
Joined: Sun Mar 29, 2020 10:23 pm

Re: How common is a false negative result?

Postby poppy86 » Sun May 17, 2020 12:18 pm

The on-call doctor basically told me to speak to my regular gastroenterologist tomorrow.

This is how my test results look:

Immunoassay (Final)
Clostridium difficile(GDH ANTIGEN-TOXIN SCREEN):NEGATIVE

Ali-Mar
Long Time Contributor
Posts: 463
Joined: Sat Mar 21, 2020 4:17 pm

Re: How common is a false negative result?

Postby Ali-Mar » Sun May 17, 2020 12:44 pm

The combination of the two tests, the Antigen test and Toxin test combined, has a very high accuracy rate of 95%. But they have to make sure they get samples to lab within the allowed time, the sample are not contaminated etc ... Most likely your test is accurate. Having said that, I don't mean to make you suspicious of the test result but might be good to know, my 1st test was a false negative using the same method, combining the two tests, my symptoms went on for 4 more weeks until my ex GI decided to test again using the PCR Toxin-Gene method which was positive and after my relapse few weeks ago we used the Combination of the Antigen and Toxin test again, and this time both were positives

https://www.health.state.mn.us/diseases ... sting.html
Male 54, contracted C-Diff on Feb 5, 2020, diagnosed on March 2nd, Took Flagyl for 8 days, Vanco for 10 days, relapsed 5 weeks post-Vanco. finished Dificid Taper on June 20 relapsed two weeks later, had the FMT on July 14th, 2020

poppy86
Regular Contributor
Posts: 197
Joined: Sun Mar 29, 2020 10:23 pm

Re: How common is a false negative result?

Postby poppy86 » Sun May 17, 2020 12:47 pm

Thank you for your reply Ali-Mar, that was very helpful. I'll be talking to my gastroenterologist tomorrow to discuss what to do. For now I'm just trying to rest. If he recommends re-testing, I'll do that, or if he orders a colonoscopy or other tests, then I'll do that too. I just really want to feel better.

poppy86
Regular Contributor
Posts: 197
Joined: Sun Mar 29, 2020 10:23 pm

Re: How common is a false negative result?

Postby poppy86 » Mon May 18, 2020 8:39 am

I got a call from my gastroenterologist's office this morning, and he'll be out of the office until later this week. But they relayed a message from him saying to continue with my taper as directed, and that he strongly suspects I have a bad case of PI-IBS along with hemorrhoids. I'll have a telemedicine appointment with him in a few days.

poppy86
Regular Contributor
Posts: 197
Joined: Sun Mar 29, 2020 10:23 pm

Re: How common is a false negative result?

Postby poppy86 » Mon May 18, 2020 10:42 am

I did have some blood work done last week, including a test for C-reactive protein. My level is 0.5, not sure what that means exactly. CRP measures the amount of inflammation occurring in the body, right? So it would be indicative of something like IBD.

beth22
Long Time Contributor
Posts: 10852
Joined: Tue Apr 07, 2009 2:23 pm

Re: How common is a false negative result?

Postby beth22 » Mon May 18, 2020 9:39 pm

A false negative when you are taking vanco is not unusual. The c reactive protein is normal as far as I know, but different labs have different scales. You can call the lab and ask what the normal scale is or maybe it is listed on your report.


Return to “Questions about Clostridium difficile”



Who is online

Users browsing this forum: No registered users and 45 guests