pcr or elisa (HIV TESTING)


dear dr.

I have actually read in this websites content that PCR are better than antibody. Is this true? Please give me piece of mind. I have tested up to 8 months using standard elisa, its negative. can i let go or should i still do a pcr?



PCR testing is generally not recommended for routine HIV screening, due to the rate of false-positives, other technical considerations and cost. You can read much more about this in the archives of this forum. Plus I'll post some additional basic information about HIV diagnostic testing below.

Your negative ELISA at eight months is definitive. HIV is not your problem. No way. No how. PCR is not recommended or warranted.

Happy New Year! WOO-HOO!

Dr. Bob

HIV Testing

April 12, 2007

What Is HIV Testing?

HIV testing tells you if you are infected with the Human Immunodeficiency Virus (HIV) which causes AIDS. These tests look for "antibodies" to HIV. Antibodies are proteins produced by the immune system to fight a specific germ. Other "HIV" tests are used when people already know they are infected with HIV. These measure how quickly the virus is multiplying (a viral load test, see Fact Sheet 125) or the health of your immune system (a CD4 count, see Fact Sheet 124).

How Do I Get Tested?

In September 2006, the US Centers for Disease Control recommended routine HIV screening of people in healthcare settings. This should result in more general HIV testing in the US. You can arrange for HIV testing at any Public Health office, or at your doctor's office. Test results are usually available within two weeks. In the U.S., call the National AIDS Hotline, 1-800-CDC-INFO.

The most common HIV test is a blood test. Newer tests can detect HIV antibodies in mouth fluid (not the same as saliva), a scraping from inside the cheek, or urine. "Rapid" HIV test results are available within 10 to 30 minutes after a sample is taken. One of these tests has produced a high rate of fasle positives. A positive result on any HIV test should be confirmed with a second test.

Home test kits: You can't test yourself for HIV at home. The "Home Access" test kit is only designed to collect a sample of your blood. You send the sample to a laboratory where it is tested for HIV.

When Should I Get Tested?

If you become infected with HIV, it usually takes between three weeks and two months for your immune system to produce antibodies to HIV. If you think you were exposed to HIV, you should wait for two months before being tested. You can also test right away and then again after two or three months. During this "window period" an antibody test may give a negative result, but you can transmit the virus to others if you are infected. About 5% of people take longer than two months to produce antibodies. There is one documented case of a person exposed to HIV and hepatitis C at the same time. Antibodies to HIV were not detected until one year after exposure. Testing at 3 and 6 months after possible exposure will detect almost all HIV infections. However, there are no guarantees as to when an individual will produce enough antibodies to be detected by an HIV test. If you have any unexplained symptoms, talk with your health care provider and consider re-testing for HIV.

Do Any Tests Work Sooner After Infection?

Viral load tests detect pieces of HIV genetic material. They show up before the immune system manufactures antibodies. Also, in early 2002, the FDA approved "nucleic acid testing." It is similar to viral load testing. Blood banks use it to screen donated blood. The viral load or nucleic acid tests are generally not used to see if someone has been infected with HIV because they are much more expensive than an antibody test. They also have a slightly higher error rate.

What Does It Mean if I Test Positive?

A positive test result means that you have HIV antibodies, and are infected with HIV. You will get your test result from a counselor who should tell you what to expect, and where to get health services and emotional support. Testing positive does not mean that you have AIDS (see Fact Sheet 101, What Is AIDS?). Many people who test positive stay healthy for several years, even if they don't start taking medication right away.

If you test negative and you have not been exposed to HIV for at least three months, you are not infected with HIV. Continue to protect yourself from HIV infection (see Fact Sheet 150, Stopping the Spread of HIV).

Can I Keep the Test Result Confidential?

You can be tested anonymously in many places. You do not have to give your name when you are tested at a public health office, or when you receive the test results. You can be tested anonymously for HIV as many times as you want.

If you get a positive HIV test that is not anonymous, or if you get any medical services for HIV infection, your name may be reported to the Department of Health.

The Centers for Disease Control (CDC) proposed in late 1998 that all states keep track of the names of HIV-infected people. This proposal has not yet taken effect.

How Accurate Are the Tests?

Antibody test results for HIV are accurate more than 99.5% of the time. Before you get the results, the test has usually been done two or more times. The first test is called an "EIA" or "ELISA" test. Before a positive ELISA test result is reported, it is confirmed by another test called a "Western Blot."

Two special cases can give false results:

Children born to HIV-positive mothers may have false positive test results for several months because mothers pass infection-fighting antibodies to their newborn children. Even if the children are not infected, they have HIV antibodies and will test positive. Other tests, such as a viral load test, must be used.

As mentioned above, people who were recently infected may test negative if they get tested too soon after being infected with HIV.

The Bottom Line

HIV testing generally looks for HIV antibodies in the blood, or saliva or urine. The immune system produces these antibodies to fight HIV. It usually takes two to three months for them to show up. In rare cases, it can take longer than three months. During this "window period" you may not test positive for HIV even if you are infected. Normal HIV tests don't work for newborn children of HIV-infected mothers.

In many places, you can get tested anonymously for HIV. Once you test positive and start to receive health care for HIV infection, your name may be reported to the Department of Health. These records are kept confidential.

A positive test result does not mean that you have AIDS. If you test positive, you should learn more about HIV and decide how to take care of your health.

This article was provided by AIDS InfoNet.