Testing for HIV

INTRODUCTION — Human immunodeficiency virus (HIV) testing is used to determine if a person is infected with HIV. Most individuals who are at the highest risk for HIV have not been tested, usually because they do not realize that they are at risk. Others avoid testing because they are worried about the possibility of a positive test result.

However, testing is encouraged because treatment for HIV is highly effective and early diagnosis can improve a person's chance of living longer and being healthier. Furthermore, knowledge of HIV status can greatly reduce the risk of transmission to others if appropriate precautions are taken.

WHAT IS HIV? — HIV is a virus that weakens the body's immune system, making it difficult to fight infections and cancers. A person who is infected with HIV may have no signs or symptoms of their illness, but can still pass the infection to other persons through sexual contact or through exposure to contaminated needles. If HIV is not treated, an infected person eventually becomes very ill and may die. The advanced stage of HIV infection is called AIDS (acquired immune deficiency syndrome).

RISK FACTORS FOR INFECTION — Patients can acquire HIV through sexual contact or through exposure to contaminated needles.

People at risk for sexual transmission of HIV include: Persons with a history of a sexually transmitted disease Sexual partners of persons who are infected with HIV Victims of sexual assault Men and women who have unprotected sex with multiple partners. Men and women who exchange sex for money or drugs or have sex partners who do Men who have sex with men who are infected with HIV.

People at risk for exposure to HIV through contaminated needles include: Injection drug users who share needles or "works" Health care workers with needlestick exposure.

Who should be tested — The United States Preventive Services Task Force (USPTF) recommends HIV testing for persons who have one or more of the above risk factors for HIV infection. In addition, the USPSTF and the CDC recommend testing for the following persons: Persons who request HIV testing Persons who consider themselves at risk for HIV Health care workers who are exposed to potentially infected blood or bodily fluids at work Donors of blood, semen, and organs (mandatory in all states) Persons who present with an AIDS-defining diagnosis (See "Patient information: Symptoms of HIV infection") Persons who received blood products from 1977 to May 1985 (before blood donations were routinely screened for HIV) Heterosexual persons with one or more sex partner(s) in past 12 months Pregnant women

Routine testing approach — In 2006, the CDC issued revised guidelines for HIV testing in adolescents and adults. These revised guidelines recommend routine voluntary HIV screening as a normal part of medical care, similar to screening for other treatable diseases such as diabetes or cholesterol. The rationale for this approach is that HIV can be detected by accurate and inexpensive testing, earlier identification and treatment can lead to decreased illness and death in those who are found to be HIV-positive, and early identification can prevent HIV transmission to other persons.

With these guidelines, the CDC also included a strategy that allows a person to "opt-out" of testing. The following would occur in this situation: A healthcare provider would explain the recommendation for HIV testing to the patient The patient would have the opportunity to ask questions. Testing would be performed unless the patient states that they do not wish to be tested.

The CDC also recommends against the use of a consent form for HIV testing. A consent form is currently required in some states to record the patient's desire to be tested,

The aim of this initiative is to minimize barriers to testing, including many people's fear of being stigmatized and health care providers' reluctance to test. Rapid HIV testing will play a key role in this new CDC strategy. (See "Rapid tests" below).

TESTING METHODS — There are several methods to test for HIV. The standard test for HIV infection requires a small sample of blood taken from a vein, and is greater than 99 percent accurate. All positive tests are confirmed with another test.

Anonymous testing — Anonymous testing allows a person to be tested without disclosing his or her identity, and is offered in some areas.

Home testing — Home test kits provide accurate and anonymous results and are available in most pharmacies. The kit requires either a small sample of blood, obtaining by pricking the finger, or a swab of the inside of the cheek.

Rapid tests — Rapid tests for HIV provide accurate results within 5 to 40 minutes. Rapid tests are useful because they do not require that a person return on another day for their results. In 2000, more than one-third of patients who were tested with standard testing did not return for a discussion of their results. In contrast, 80 percent of those patients who tested HIV-positive with rapid testing later sought medical care [1].

TESTING PROCEDURE

Frequency of testing — Initial testing for HIV can be done at any time, but may need to be repeated if a person is concerned about recent exposure. Repeat testing is usually recommended at 6, 12, and 24 weeks after a suspected exposure. (See "Patient information: Symptoms of HIV infection").

Periodic testing is recommended for persons who are at risk for infection. (See "Risk factors for infection" above). Most healthcare providers recommend repeat testing every 6 to 12 months for such persons.

In addition to testing, individuals should learn about ways to prevent infection with HIV. This includes encouraging sexual partners to be tested, use of a latex or polyurethane condom with every sexual encounter, avoiding drugs or alcohol that can affect judgment about sexual activities, and avoiding needles and syringes that have been used by other IV drug users and avoiding sexual intercourse (abstinence).

TEST RESULTS — Test results are reported as being positive, negative, or indeterminate. The chance of having a negative result despite being infected with HIV (false negative) or a positive result despite having no evidence of HIV infection (false positive) is very low. The most common cause of a false positive result is human error in performing the test or reporting the test result. All false positive results are easily resolved by getting other tests that confirm the positive result or prove that the person is not infected. The most common cause of a false negative result is being tested before HIV antibodies are made. A person should inform their health care provider if they may have been exposed recently; in this case a test for the presence of virus in the bloodstream may also be needed. Persons should be retested at 3 and 6 months after the possible exposure. An indeterminate result occurs when a person's result is not clearly positive or negative. The final result usually depends upon a person's risk of having HIV. In persons at low risk for HIV infection, approximately 1 in 5000 results (0.0002 percent) are indeterminate. This type of laboratory result requires additional counseling and diagnostic testing, as determined by an HIV specialist.

While awaiting the results of further testing, the person should take precautions to avoid transmitting their potential infection to others. This includes discussing the possibility of infection with any sexual partners and use of a condom with every sexual encounter. Sharing of razors, toothbrushes, and any injection drug equipment (needles, syringes) should also be avoided.

SUMMARY Most individuals who are at the highest risk for HIV have not been tested usually because they do not realize that they are at risk for HIV. Others avoid testing because of anxiety about the possibility of a positive test result. However, testing is encouraged because treatment for HIV is highly effective and early diagnosis can improve long-term outcome. Furthermore, knowledge of HIV status can greatly reduce the risk of transmission to others. HIV is a virus that weakens the body's immune system, making it difficult to fight infections and cancers. A person who is infected with HIV may have no signs or symptoms of their illness, but can still pass the infection to other persons through sexual contact or through exposure to contaminated needles. If HIV is not treated, an infected person eventually becomes very ill and may die. There are several methods to test for HIV. The standard test for HIV infection requires a small sample of blood taken from a vein, and is greater than 99 percent accurate. All positive tests are confirmed with another test. Anonymous, home, and rapid tests are also available. Initial testing for HIV can be done at any time, but may need to be repeated if a person is concerned about recent exposure. Repeat testing is usually recommended at 6, 12, and 24 weeks after a suspected exposure. The accuracy of HIV blood testing is high, greater than 99 percent. Test results are reported as being positive, negative, or indeterminate. The chances of having a negative result despite being infected with HIV (false negative) or a positive result despite having no evidence of HIV infection (false positive) are very low.

WHERE TO GET MORE INFORMATION — Your healthcare provider is the best source of information for questions and concerns related to your medical problem. Because no two patients are exactly alike and recommendations can vary from one person to another, it is important to seek guidance from a provider who is familiar with your individual situation.

This discussion will be updated as needed every four months on our web site (www.patients.uptodate.com). Additional topics as well as selected discussions written for healthcare professionals are also available for those who would like more detailed information.

A number of web sites have information about medical problems and treatments, although it can be difficult to know which sites are reputable. Information provided by the National Institutes of Health, national medical societies and some other well-established organizations are often reliable sources of information, although the frequency with which they are updated is variable. Centers for Disease Control and Prevention (CDC)

Toll-free: (800) 311-3435
(www.cdc.gov)
CDC (Centers for Disease Control and Prevention) National AIDS Hotline

English: (800) 342-2437
Spanish: (800) 344-7432
CDC National Prevention Information Network (NPIN)

Toll-free: (800) 458-5231
National Institute of Allergy and Infectious Diseases (NIAID)

(www.niaid.nih.gov)
HIV/AIDS Treatment Information Service

Toll-free: (800) 448-0440
(www.hivatis.org)
AIDS Clinical Trials Information Service (ACTIS)

Toll-free: (800) 874-2572
(www.actis.org)


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Use of UpToDate is subject to the Subscription and License Agreement. REFERENCES 1. Wright, AA, Katz, IT. Home testing for HIV. N Engl J Med 2006; 354:437.
2. Greenwald, JL, Rich, CA, Bessega, S, et al. Evaluation of the Centers for Disease Control and Prevention's recommendations regarding routine testing for human immunodeficiency virus by an inpatient service: who are we missing?. Mayo Clin Proc 2006; 81:452.
3. Updated U.S. Public Health Service Guidelines for the Management of Occupational Exposures to HBV, HCV, and HIV and Recommendations for Postexposure Prophylaxis. MMWR Recomm Rep 2001; 50:1.
4. Chou, R, Smits, AK, Huffman, LH, et al. Prenatal screening for HIV: A review of the evidence for the U.S. Preventive Services Task Force. Ann Intern Med 2005; 143:38.
5. Chou, R, Huffman, LH, Fu, R, et al. Screening for HIV: a review of the evidence for the U.S. Preventive Services Task Force. Ann Intern Med 2005; 143:55.