Human Immunodeficiency Virus

Diagnosis

If you are concerned that you may have been exposed to HIV, a simple blood test can determine if you have been infected. The standard HIV blood test is designed to detect antibodies to the HIV virus in your blood. At least 95% of people will develop antibodies to HIV within six months of infection. A test performed too soon after infection may give a false-negative result.

The most commonly used blood test is called an ELISA (enzyme-linked immunosorbent assay). The test is very sensitive, but occasionally it will give a false-positive result. Whenever an ELISA test comes back positive, a second more specific test known as a Western blot is performed to confirm the results. Both ELISA and Western blot tests require that you give blood during a first visit, and then return to get the results from your doctor one to two weeks later.

Rapid screening tests have also been developed that provide results in 15 to 30 minutes, and require only a single office visit. A drawback to rapid testing, however, is that positive results will not be confirmed with a Western blot. Consequently, the rate of false positives is higher for rapid screening tests than for standard (ELISA plus Western blot) testing.

Home collection kits for HIV testing are also available. There are many different tests available; however, only the Home Access Express HIV-1 Test System (a product of the Home Access Health Corporation) has been approved by the FDA. To perform this test, a person pricks a finger and blots the blood onto a piece of paper. The sample is then mailed to a lab, and the results are provided over the phone several days later. In clinical studies, this test was able to identify 100% of known positive samples, and 99.5% of HIV-1 negative samples.

If your blood test is positive, your doctor will take a medial history to help determine the health of your immune system. When you first seek treatment for HIV, your doctor will take a medical history to identify factors that may affect the progression of your disease. The medical history will help your doctor to determine the overall health of your immune system, and thus will inform important treatment decisions. The average time for untreated HIV disease to progress from infection to development of AIDS is 10 to 11 years, so if you were infected soon before your positive test, you are unlikely to develop symptoms in the near future.

You doctor will ask you questions to identify:

• Symptoms related to HIV infection

• Current medications you are taking and any allergies to medications

• Past history of tuberculosis, hepatitis, or sexually transmitted diseases

• Previous treatment with antiretroviral drugs

• Previous immunizations

• History of substance abuse

Your doctor will perform a comprehensive physical examination. The most common symptoms of HIV infection your doctor will look for include weight loss, a white coating on your tongue that indicates a yeast infection (candidiasis or thrush), and signs of other infections that wouldn't normally occur in people with healthy immune systems.

Your doctor will order additional blood tests to determine the health of your immune system and estimate the stage of your HIV infection. One test is designed to determine the number of CD4 cells in the blood, and the second is a test for HIV viral load. These tests help to stage the infection, determine when to begin or change antiretroviral therapy, and to monitor how well a particular drug or drug combination is working. The lower the viral load, the lower the risk of disease progression.

Both CD4 counts and viral load testing will generally be done every three to four months after diagnosis to monitor the progression of the disease.

Prevention and Screening

The risk of contracting HIV can be reduced through sexual abstinence or by engaging in safer sexual practices. HIV is most commonly transmitted through exchange of bodily fluids during intercourse or other types of sexual behaviors. Abstinence is the only way to completely eliminate the risk of contracting HIV through sexual encounters. Engaging in safer sexual practices, however, is a more realistic way for people to reduce their risk of contracting HIV.

Latex and polyurethane condoms provide an impenetrable barrier to HIV, and when used with every sexual encounter, provide effective prevention against infection. Condoms should only be used before their expiration date, and when no obvious signs of defects or damage are visible.

The U.S. government's Centers for Disease Control and Prevention recommend the following:

• Use a new condom with each act of intercourse.

• Carefully handle the condom to avoid damaging it with fingernails, teeth, or other sharp objects.

• Put the condom on after the penis is erect and before any genital contact with your partner.

• Ensure that no air is trapped in the tip of the condom.

• Ensure adequate lubrication during intercourse, possibly requiring use of lubricants such as KY Jelly or glycerine. Never use oil-based lubricant such as petroleum jelly, shortening, mineral oil, massage oils, body lotions, or cooking oil. Oil can weaken latex, leading to tears in the condom.

• Hold the condom firmly against the base of the penis during withdrawal. Withdraw while the penis is still erect to prevent slippage.

Having a monogamous sexual relationship with an uninfected partner can dramatically reduce your risk of contracting HIV. The primary risk in these cases, however, is that one or both of the partners may not be completely truthful about having sex outside the relationship with people who could be infected with HIV.

Partners considering a monogamous relationship can be tested to confirm their HIV status, but they should remember that the HIV antibody test may miss infections that occurred six months or less before the test was performed.

Avoiding high-risk sexual practices such as anal intercourse can reduce the risk of HIV transmission. Unprotected anal intercourse is considered to carry the highest sexual risk of HIV transmission. Microscopic cuts or abrasions that occur in both partners during anal intercourse allow the virus to get directly into the bloodstream. Unprotected vaginal intercourse is also considered to carry a relatively high risk of HIV transmission.

Use safer-sex precautions if you engage in oral sex. While it was commonly thought that unprotected oral sex posed a lower risk for HIV transmission than did unprotected vaginal or anal intercourse, a recent study of 122 people with a primary HIV infection revealed that 6% of that group had been infected through oral sex. This study refutes the previous notion of unprotected oral sex as “safe,” and underscores the importance of consistently engaging in safer sex practices.

Intravenous drug users can reduce their risk of contracting HIV by not reusing or sharing needles. Half of all new HIV infections in the U.S. are estimated to occur among people who inject illegal drugs. Because many of these infections could be prevented if drug users did not use contaminated needles or syringes, needle exchange programs have been set up in more than 80 cities in 38 states in the U.S. The details vary, but the programs generally distribute clean needles and syringes, safely dispose of used ones, and offer referrals for drug treatment and counseling.

The risk of passing HIV from a mother to her child during pregnancy or birth can be reduced through drug treatment [Table 3]. In 1994, a pivotal clinical trial demonstrated that a three-part drug regimen of zidovudine (AZT) could reduce the risk of HIV transmission from the mother to her child by 70%.

Since 1994, however, several new drugs have been developed. Current treatment recommendations for adults and adolescents include using combination therapy, which has proved to be more effective than AZT alone. While this new combination therapy would be most effective for treating a pregnant woman, its effectiveness for preventing transmission to the child remain unclear. Taking these factors into account, The U.S. Public Health Service Task Force currently recommends that physicians offering combination therapy as an option to HIV-infected pregnant women fully inform them of its potential benefits and risks. The Task Force further recommends that pregnant women consider delaying therapy until 10 to 12 weeks into pregnancy, because early pregnancy is the period in which the fetus is most susceptible to drug-induced birth defects.

Adapted from the U.S. Public Health Service Task Force Recommendations for the Use of Antiretroviral Drugs in Pregnant Women Infected with HIV-1 for Maternal Health and for Reducing Perinatal HIV-1 Transmission in the United States, Feb. 25, 2000.

Using formula rather than breast milk can reduce the risk that an infant will contract HIV from breast milk. HIV can be passed from a mother to her child through breast milk. As many as 40% of pediatric HIV infections in developing countries are thought to be caused by breast milk, the risk increasing the longer the child is breastfed. In the U.S. and other industrialized countries, national health authorities recommend that HIV-positive women not breastfeed their infants to reduce the risk of virus transmission.

AZT treatment directly after a known exposure may stop HIV infection from developing. Healthcare workers exposed to HIV-contaminated blood through needlesticks have long been treated with AZT to prevent an HIV infection from becoming established. This treatment is known as postexposure prophylaxis, or PEP.  Most forms involve using one or more drugs within 72 hours of a possible exposure, continuing for a period of 4 weeks.

Preliminary evidence shows that PEP is also effective after sexual or drug-related exposure to HIV. In a recent San Francisco study, 400 participants were given PEP after known HIV exposures. None of those treated had developed an HIV infection after 6 months.