Viral PCR test for HIV

March 1, 2006 8:38 AM

Is it a good idea at the moment to have a viral PCR test for HIV 10 days after being exposed to risk?

I've done something stupid and risky and need to get checked out. A local clinic is offering a viral PCR test 10 days after exposure. I feel that it would be good to get a negative result soon, although I will confirm with standard tests at 3 and 6 months.

This site seems to approve of the test and says it's accurate, but suggests 48-72 hours.

This site doesn't recommend it (search for pcr in the page).

Do you think I should get it, and if so any ideas on how long I should wait?

My email is [e-mail] if you'd rather stay anon.

posted by anonymous to health (15 comments total)

If I were you, I'd forget about the viral PCR test and head over to the local clinic immediately for STD prophylaxis. The prophylaxis is a high-dose antibiotic, which won't help for HIV, but it will help for other bugs. Go get an HIV test in 6 months, it won't kill you to wait that long.
posted by crazycanuck at 8:56 AM on March 1, 2006

The negative result of such a test is not meaningful - even the page that you link that "approves" of it (broken link, by the way - try here) notes that negatives need to be confirmed 13 weeks later by ELISA.

If it comes up positive, you're positive; if it comes up negative, you are in a 'wait and see' mode. In other word, such a test has a high Predictive-value-positive, but a low predictive-value-negative.

You should go to your local clinic for counseling, not a test. The counseling will advise you what test to get, when to get it, how to interpret the results, how to deal with your anxieties in the meantime, et cetera.
posted by ikkyu2 at 8:58 AM on March 1, 2006

You don't want to hear this, you want consensus from AskMe, but I'm going to give this answer because it's the right one:

1) ok, what crazycanuck said, too... but...

2) ask your doctor what the right course of action is. his / her job is to keep up on these things and give you guidance.

I hope all is well with you and that you're free and clear.
posted by twiggy at 8:59 AM on March 1, 2006

Sure. If you're worried about it enough, and the cost isn't prohibitive. I just checked with my Medical Director (I work in an STD/HIV clinic), and she suggested waiting until 14 days, which is the outside of how quickly a PCR will show results. It is the quickest test.

If it comes back positive (which it won't), I would suggest immediately trying to get into an acute seroconverters study at a local HIV clinic. Probably at a University. The science behind what to do with people who are in the process of forming their immune response to HIV is very emergent. There is some evidence, and much speculation, that getting onto anti-virals early will help with setting the immune system setpoint, which is to say that one would have a healthier immune reconstitution post-infection.

If you know that you were exposed, you might be able to convince someone to give you anti-retroviral prophylaxis if you act quickly. I would call the nearest dedicated HIV clinic. (I have no idea if they will go for this.)

General STD prophylaxis is not really standard of care, at least in the US. It would actually be pretty irresponsible to offer someone anti-biotics for something that they might not have. More to the point, none of the STDs that would be cured by such an approach are dangerous to have for a little while. Long term STD infection without treatment can be dangerous (mostly for women), so even if you develop no symptoms I'd suggest getting tested when you go to get HIV tested. The viral STDs that stick around (Herpes, or HPV/warts) are not treated by antibiotics anyway.

My email is in my profile if you have any other questions regarding risk or anything else, or if you just want to hash it out. I will guarantee not to share any emails you send.
posted by OmieWise at 9:09 AM on March 1, 2006

ikkyu2 writes "If it comes up positive, you're positive;"

ikkyu2 is correct about the wait and see aspect, but is, I think, overlooking the emerging research on treating acute infection. That would be a reason to act on a positive result.

The local clinic will most likely counsel waiting 3-6 months for the ELISA/Western Blot test. That is the standard (by which I mean US gov't approved/standard of care) counseling information. Some of this has to do with the indeterminacy, some has to do with the relative cost of the tests. It's your money and peace of mind.

(On the whole, though, and I perhaps should have included this in my first answer, exposure and infection do not follow in a one to one way. Recent evidence suggests, for instance, that about 50% of new infections occur due to exposure to someone who is themselves newly exposed, probably so newly exposed that their own antibody tests would come back negative. This is because chance of infection seems to be tied to viral load, and people have high viral loads immediately after infection, which then decrease dramatically in most people as the immune system responds. An awful lot depends on the type of exposure, the viral load of the infected person, the health of the exposed person, etc. Certainly it is true that unprotected sex and even needle sharing are risks, but do not translate (especially if the other person isn't known to have HIV) into necessary infection. Waiting for the standard test is not a bad idea, although it might be uncomfortable.)
posted by OmieWise at 9:20 AM on March 1, 2006

I think you need to address the reason why you want to take it. If it is for peace of mind, taking the test now is premature. If it is negative, you will not have peace of mind because of a high rate of false negatives at this early time. False positives are not higher at this point, so if you are positive, you probably carry the virus.

What may help you is knowing the odds. If you have a single instance of unprotected sex with someone who is HIV positive but not necessarily having a high HIV load, the possibility of infection is still quite low. Less than 1 in a 100 (around 1 in a 100 for anal, 1 in 200 for vaginal, pretty low for oral as in case studies of oral only transmission get published). If the stupid behavior you refer to is needle sharing with someone who is HIV positive, then the odds go up. (These are from memory, but I think it is about 1 in 50.)

Why does anyone catch HIV then? Multiple exposures (these odds are back extrapolated) or exposure to those who have high virus loads (below).

These odds differ greatly depending on whether the person has a high amount of virus in his/her blood seminal/vaginal fluids. This usually happens either shortly after that person has been infected or late in disease with therapy failure (or not taking therapy).
posted by dances_with_sneetches at 9:46 AM on March 1, 2006

Just to chime in - I would ask a health professional but I wouldn't ask my doctor, assuming you have health insurance or you give your doctor your real name. Even if you're uninsured now (perhaps particularly if you're currently uninsured) you sign over rights for them to poke through all your past records when you sign up.

No matter where you are - and I wish you'd said - there are almost certainly clinics that will do testing for you nearby. What level of anonymity you can get will vary and may depend on state law. Personally I am very cynical about medical privacy and the future thereof and if I thought there was a possibility a test would come back positive I'd move heaven and earth to keep from getting my name attached to the test in any way, even if the testing agency promised privacy. After all, stored data may be private now but not later.

Good luck and my best hopes to you.
posted by phearlez at 10:28 AM on March 1, 2006

Just to take this down to bare tacks...

By risky, do you mean that you (had sex|shared needles|whatever) with someone you -know- to be infected? If not, then why not take the steps to find out if that person IS infected? If not, then the mental pressure should be eased considerably.
posted by Kickstart70 at 12:10 PM on March 1, 2006

What Kickstart70 said. Ascertain--as well as possible, given the recent research that OmieWise alluded to--what the HIV status of the other person/people is. Bear in mind also that HIV prophylaxis treatment is, as far as I know, only offered to healthcare professionals. It's--again, from what I know--an extremely debilitating regime of high-dose antiretrovirals.

The only thing the PCR can tell you at this point is if you have contracted HIV. So it lessens some of the waiting time, but only if it comes back positive. If it comes back negative, you still have to get the three and six month tests anyway.
posted by dirtynumbangelboy at 12:53 PM on March 1, 2006

ikkyu2 is correct about the wait and see aspect, but is, I think, overlooking the emerging research on treating acute infection.

Where did you come up with that? Go back and read my answer again. You'll see I never touched on that topic, nor did I give any advice except "go to a clinic for counselling."

I think you mentally conflated my answer with someone else's.
posted by ikkyu2 at 5:21 PM on March 1, 2006

If you know the person to be infected, or even if you don't, you should get to a doctor immediately. Really. As soon as you humanly possibly can.

Because there is something called post-exposure prophylaxis that you can take. It is for HIV. It's what they give health care workers who've had needle sticks.

It's basically a short course of antiretroviral drugs that can potentially keep you from being infected with HIV if you have been exposed. You should look into it. But look into it quickly, because its efficacy decreases with every hour that passes up to, I think, 72 hours.

Any health care workers out there who know what they're talking about who can say whether or not this is a situation where you would be able to get PEP?
posted by jennyjenny at 6:36 PM on March 1, 2006

Postexposure prophylaxis isn't routinely recommended in all cases of unprotected sex. Recall that the medicines are not benign - they can cause harm - and that a lot of people have unprotected sex every day, without catching AIDS.

Now, if someone came to me and said, "I just shared needles with someone I know to have a viral load of 750,000, and I'd like not to seroconvert?" would that person get PEP? Almost certainly. In between, there is a range in which clinical judgment is used. This sort of judgment is not exercised with regard to anonymous posters over the internet - a person should visit a professional to get a customized recommendation for themselves.
posted by ikkyu2 at 8:33 AM on March 2, 2006

ikkyu2 writes "ikkyu2 is correct about the wait and see aspect, but is, I think, overlooking the emerging research on treating acute infection.

"Where did you come up with that? Go back and read my answer again. You'll see I never touched on that topic, nor did I give any advice except 'go to a clinic for counselling.'"

Hey, I meant no offense, I did, in fact, mean that you did not address the reasons why a positive test might be more than negatively meaningful.

Most clinics will counsel waiting for the Elisa/WB, but there are funding issues involved in that counseling that don't really address the questions asked by anon.
posted by OmieWise at 9:00 AM on March 2, 2006

Yeah, I know you didn't mean any offense. You're OmieWise, which is to say, omnibenevolent :)

Counselors use guidelines that are developed for many different reasons. Either you trust the folks who developed those guidelines, or you second-guess them. I tend to lean in favor of trusting them, because they are thinking from a public health perspective.

The bottom line is that the test doesn't change anything. If you're infected, you're infected; the test doesn't change that. Most folks who turn up positive on a day 10 test were infected before the event that prompted them to get infected. That's because people who do risky behaviors tend to be the people who did risky behaviors in the past.

The more I learn, the more I am against the patient trying to become an expert on whatever he or she thinks he has today. Patients can't become experts. They can consult experts, and they should do.
posted by ikkyu2 at 10:41 PM on March 2, 2006

ikkyu2 writes "The more I learn, the more I am against the patient trying to become an expert on whatever he or she thinks he has today. Patients can't become experts. They can consult experts, and they should do."

Good point. Let me add to what I wrote above as I was just at a presentation yesterday, as fate would have it, about a new NIH funded study re: acute seroconversion. All of this is just for the sake of information, although point #3 is a big caveat to what I've written before:

1) The study is using viral load tests to determine if people presenting in what might be acute HIV infection are actually HIV positive. The study director assured me that after two weeks they feel very confident that this test is accurate, certainly for positives. Negatives as well, although negatives should be confirmed by Elisa after 6 months just to be on the safe side.

2) I asked, out of curiousity prompted by this thread, about the use of Elisa's for HIV testing, and he confirmed my own understanding (I'm already a trained HIV pre- and post-test counselor), which is that cost is the main factor here. And Elisa costs $3, and a PCR costs $80. Those are costs for a large public health lab without factoring in overhead. (A Western Blot runs close to $80 as well, but is not run except in the case of a positive Elisa.)

3) Contrary to what I think I might have implied above, there have been no randomized trials of giving anti-viral meds to people with acute HIV infection. There are several studies around the country gearing up for such trials right now, including this one in which I'm (very) tangentially involved. The supposition, and indeed some doc's clinical direction, is that treating for a limited period during acute infection will result in a healthier immune system over the long term and a lower viral load set point for new HIV patients. This is important because viral load is the best predictor we have of future disease progression. In other words, it's predictive. There are more than a few docs who are starting to treat acute HIV infection clinically, but no studies yet that follow patients long term.
posted by OmieWise at 10:21 AM on March 3, 2006