Author Topic: FELV Positive with ELISA Test now Negative with IFA Test  (Read 774 times)

Offline Judecat (Paula)

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Re: FELV Positive with ELISA Test now Negative with IFA Test
« Reply #7 on: November 21, 2017, 03:03:05 AM »
Sorry Merlin tested positive for FIV, but came back clear on FeLV, so I have no experience of this. He wasn't tested further than bloods sent up to Glasgow which also came back negative. But that was weeks rather than months.

Due to his injury he only goes as far as the back garden so only has restricted access to cats other than my own. For those who don't know he has a club paw due to being caught in, (the vet thinks ripping his way out of a snare), taking off the pads on a forefoot. so he walks three legs and a dot.

My other cats were (are) vaccinated so I don't worry about them.

Sorry I can't be of more help.
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Offline Sue P (Paddysmum)

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Re: FELV Positive with ELISA Test now Negative with IFA Test
« Reply #6 on: April 28, 2017, 13:20:13 PM »
Desley, you're a star - thanks for that.  Am sure this will be helpful to siami

Offline Desley (booktigger)

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Re: FELV Positive with ELISA Test now Negative with IFA Test
« Reply #5 on: April 28, 2017, 12:50:49 PM »
I always forget the names of the tests, but basically the in-house one has a high percentage of false positives, the one done by the lab is the most accurate. The reason is that cats can come into contact with FeLV, but shed the virus, if they do that, they will be immune for life - it can take up to 3 months for them to shed the virus, although you don't know when they came into contact with it, so it could have been 2 months before testing. I'm fairly sure that if the lab one is negative, they are negative, it's a very low percentage of false negatives

I can't find the Uni website I used to use, but this might help

When a virus or any other foreign invader tries to enter the body, the immune system will produce several types of antibodies. These attack the invader and try to damage it so that it does not become overwhelming. For the leukaemia virus, this process (immunity) takes about four to 12 weeks. During this time the virus is only in the bloodstream. If immunity does not develop, it establishes in the bone marrow and the cat is infected for life.

The simple “in house” test is called the p27 test because it looks for a fragment of virus called the “p27 antigen”. This appears in the blood following infection. If a healthy cat tests positive, then repeating the test increases the accuracy. Sending a sample to a commercial laboratory for a different test makes it more accurate still. A cat that tests positive on two “in-house” tests is likely to be a true positive, but ideally this should still be confirmed by commercial testing.

However, testing while immunity is developing can show a cat in the process of overcoming infection as positive for FeLV, even if the cat is eventually going to develop immunity. Because of this, a single positive test result is not proof of infection in a healthy cat. If necessary, a special test can be done on healthy “positives” to look for antibodies of a type likely to be effective in providing immunity. These are called “virus‑neutralising antibodies”.

False negatives can also occur occasionally, in which the test is clear when your cat is actually infected. To be truly confident that a healthy cat does not have the virus, a retest should be done after a 12-week interval. This detects those in the early stages of infection at the first test, which did not then develop immunity. A false negative can sometimes occur in a sick cat as well. If there is clinically a strong suspicion of FeLV infection in a “negative” sick cat, commercial testing may be worthwhile.

Occasionally, a cat is persistently positive on the p27 test but negative on the commercial tests. It is thought that some of these cats may have “latent” infection, with the virus hidden in their body (usually in the bone marrow). As long as the commercial tests are negative, they are not a risk for other cats, but the situation should be monitored.
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Offline Sue P (Paddysmum)

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Re: FELV Positive with ELISA Test now Negative with IFA Test
« Reply #4 on: April 28, 2017, 11:23:55 AM »
Didn't mean to leave Mollie and Leo out of the Welcome to Purrs, so just for them:   :welcome: :welcome:

How old are your babies, and what are they like?   :)

Am hoping Liz, Paula or Sheila will see this thread as all have experience with this.   :hug:

Offline siami

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Re: FELV Positive with ELISA Test now Negative with IFA Test
« Reply #3 on: April 28, 2017, 11:07:04 AM »
Thank you for your welcome.  I live in France now, previously on the Essex coast.

Offline Sue P (Paddysmum)

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Re: FELV Positive with ELISA Test now Negative with IFA Test
« Reply #2 on: April 28, 2017, 10:59:14 AM »
Hello Siami - welcome to Purrs, although very sorry it's at such an anxious time for you. :welcome:

Apologies, but I know little about this.  Am sure that other members will be along who can shed some light on it for you.  We have members who are knowledgeable in this regard who may be able to advice.  I know there is a lot of concern over false positives and false negatives, so fully understand your need for reassurance.

Where are you Siami?  Are you in the UK or elsewhere?  I understand different areas have different views on testing and the processes involved, so it may be helpful to know your general location.

Saying hi to Charlie too  :welcome:

Offline siami

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FELV Positive with ELISA Test now Negative with IFA Test
« Reply #1 on: April 28, 2017, 10:50:40 AM »


30 days ago Charlie had a faint positive result on the vet's in-house ELISA test and on Tuesday the vet took some more blood while Charlie was being castrated and sent it off to a lab for the IFA test. This came back negative. After whooping for joy, I researched some more and found it was a bit early to celebrate as the second result could be a false negative. I can't let Charlie mix with my other cats until I am as near 100% sure as it's possible to be.

If I've understood correctly and the ELISA test shows the virus in the blood and the IFA test shows the virus in the bone marrow, should I have the ELISA test re-done now to hopefully confirm Charlie is clear?
Thanks in advance for any advice.  My vet can't help as she seems to know very little on this subject.
     


 


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