How often do false positves happen?

[willy851]

I recently got tested for std's and hcv was one of them. I had a sexual encounter three months prior and wanted to get checked. The test came back and said not infected with HCV unless recent infection is suspected. The level was .1 from 0 to .9 they didn't do any other test on it to prove it was HCV. The Doc said not to worry, but I am still a basket case. I thought it was hard to get HCV from sex.
I performed oral without protection but used a  condom otherwise.

In reading I find that these tests come back false positive often. My question is how often and how worried should I be?


Thank you for any insight!

[Bill1954]

Antibody tests are subject to false positive results, however infrequently; I do not know the statistics offhand, though. Antibody tests do not test directly for the virus, but detect antibodies that our immune system produces in response to viral exposure. In other words, even if you tested positive/reactive via antibody test, you still might not have an active case of HCV, only exposed at one point or another. About 15-30 % of those exposed will clear the virus (seroconvert) without medication.

If for some reason this is still causing you grief, you might persuade your health care provider to order a HCV RNA PCR test. While more costly than the various antibody tests, this test is extremely conclusive for the presence of active HCV infection, and can detect the presence of virus within days or weeks of exposure rather than months. Due to the added expense, many doctors are hesitant to order this without further indication of infection, but it may be worth it for your peace of mind. Although you didn’t mention sexual preference-- HCV does not transmit easily through heterosexual contact, but it probably can happen on occasion.

I hope this info helps a little; take good care, and put a sock on it next time!

Best to you, Bill

Ooops, I finished reading your post; the chances of transmission from oral sex is thought to be almost nil… put a sock on your tongue?

[mremeet]

I wouldn't be worried if I were you, the odds of you getting it the manner you described are very very low. But I would follow up with another antibody test in another 3 months just to make absolutely certain, and for your own peace of mind.

[wyntre9]

When I was first told that I might have the virus back in Septemebr my Dr. made me repeat the test coz he said there was a 5% chance of false positive readings.  

When the repeated tests still showed the virus he referred me to a gastro.

The gastro did other tests that confirmed the positive reading and then scheduled me for biopsy and endoscopy.

[jmjm530]

A lot of folks here are positive about lots of things that turn out to be false under scrutiny -- so in that sense false positives are quite frequent.

In the sense of testing, I think what you're referring to is a false negative, but like stated, it seems unlikely you have it. You can always test again at a later time if it will make you less anxious.

[jboyhk]

willy,

correct me if i am wrong but you said you had a .1 in a ref range of 0-.9.

That means you tested negative not positive. A positive would be over .9.

[Jakied]

If I am reading your numbers correctly, you tested .1, not 1.0, on the antibody test, three months after exposure.  this is a neg outcome.  In my opinion, you have rounded third and are headed for home free.  The window period for Hcv is the same as Hiv.  A three month neg is VERY reliable, 6 months is conclusive.

Put your mind at ease.  Get another test at three months, It will be neg (99% sure of that) and then forget it and move on with life.  Don't become a ' worried well.'

Hcv can be transmitted by sex but happens only rarely.  Idu, blood transfusions and organ transplants are the common methods of transfer.  With sex, man to woman transmission is more common than woman to man.

[wyntre9]

"A lot of folks here are positive about lots of things that turn out to be false under scrutiny -- so in that sense false positives are quite frequent."

There IS such a thing as a FALSE POSITIVE!  It's listed right on the lab report!  Plus my doctor went over the numbers with me to try and reassure me that maybe I DIDN'T have the virus.

OK, maybe I misunderstood the technically misquoted question but I'm neither an expert nor a mind reader.

"In the sense of testing, I think what you're referring to is a false negative"

They also exist, according to my Doctors.

I'm just glad to hear that the poster is probably negative.  What a relief for him.

[wyntre9]

It sounds like you're in pretty good shape but here's the quote from my original
Hepatitis Panel.

HCV Ab 43.3 High
Positive
Indicates past or present HCV infection

Samples with high S/CO ratios (>9.9) confirm positive (95%)

BUT <5 out of a hundred might represent false-positives.

Good luck.

[Bill1954]

Willy; thanks for the topic. I hope you find this thread, I find it interesting. If you indeed turn out positive for HCV, I seriously doubt it would have been from the encounter you described above. Good luck!

Jim, Wyntre, Jakied, all—

This is a good topic. Most of us are diagnosed and have already confirmed by nucleic acid testing prior to our educational process in this disease, so antibody testing sort of falls by the wayside; at least that has been my experience, anyway.

I culled this page from Medscape; maybe it will help to sort things out a little. It says in part: “…EIA testing offers several distinct advantages in the diagnostic setting, because these assays are easy to perform, are relatively inexpensive, and have high sensitivity. A positive EIA-antibody test result requires a second confirmatory assay to make the diagnosis of hepatitis C. False-positive EIA test results may occur in low-risk patients and in patients who have underlying autoimmune diseases. These patients may benefit from RIBA testing to differentiate a false-positive from a true-positive test result.
Recombinant immunoblot assays. These tests are supplemental assays to EIA testing. RIBA test results are interpreted as positive if 2 or more antigens are positive, interpreted as indeterminate if 1 antigen is positive, and interpreted as negative if all antigens are negative. RIBA testing is not more sensitive than EIA testing, but a RIBA test can be used to distinguish between a false-positive EIA test result and previous exposure to hepatitis C. A third-generation RIBA test (RIBA-3) is licensed in the United States. This assay incorporates the NS5 antigen to the standard antigens used in RIBA-2. (Figure 3). This third-generation test produces a reduced number of indeterminate results and is more specific than the RIBA-2 assay…”.
It goes on to discuss other test methodology, and is fairly informative. From: http://www.medscape.com/viewarticle/416562_6

As always, I appreciate your comments—

Bill

[wyntre9]

Thanks Bill.

I was just trying to offer my (admittedly) limited knowledge and respond to Willy and share my experience.

The article you quoted sounds like the kind of tests I had in September 2006.  For me, from initial diagnosis to tx has been a blur - 2 to 3 months, max.

Thanks for helping to clarify what I was (evidently poorly) trying to relay.  That's it, exactly.  Based on the first tests, which COULD have been false-positives, others were ordered to confirm results, referral to gastro came next, blahblahblah and now I'm up to shot 14.

I just found this comment:

"A lot of folks here are positive about lots of things that turn out to be false under scrutiny -- so in that sense false positives are quite frequent."

particularly galling, as it seemed to be directed at me, and I don't get insulted too easily.

Guess since I don't know "Forum-Speak" I should just keep my mouth shut.

I give up.

Don't think I'll post any more of my own stats and ask for advice as I might say it wrong.

Silly me.  I thought that's what this forum was for; to try and understand.

[mar1249]

Hi,
I don't have Hep C but, my husband does.  He was in a near fatal car accident in 1989.  He was given many transfusions.  2 years later we were told about the Hep C.

5 Years later he was still on the interferon shots.  He has been in remission for about 10 years.  He goes yearly for the quanatitve blood test.  About 8 years ago we had a false/positive.  This year it showed the virus was back.  According to the nurse he was right on the border.  1.9 shows positive he was 2.2.  Could this still be a false/positive?

We went for re-test and he also needed to get a liver function blood test.
He is keeping a positive attitude.  I am the one who is going nuts.  
I assuming you are on meds correct?  What do you know about the ribavin and pegainterferon?  Any help you can give me would be helpful
thanks

[copyman]

I know your question was to bill but i will take a shot at the question as well. once you have HCV you will show antibodies. maybe this is what happen with your husbands test. to be sure he should have a PCR test done. good luck

[damosaab]

just reading your threads about false positives can any body explain in simple terms wat that result means

[HCA]

It's an antibody test-he will always test positive for antibodies.
The virus does not come back after all these years.
There is nothing to worry about.