Human Immunodeficiency Virus Antibodies

This test detects antibodies to human immunodeficiency virus (HIV) in serum. HIV is the virus that causes acquired immunodeficiency syndrome (AIDS). Transmission occurs by direct exposure of a person's blood to body fluids containing the virus. The virus may be transmitted from one person to another through exchange of contaminated blood and blood products; during sexual intercourse with an infected partner; when I.V. drugs are shared; and from an infected mother to her child during pregnancy or breast-feeding.

Initial identification of HIV is usually achieved through enzyme-linked immunosorbent assay. Positive findings are confirmed by Western blot test and immunofluorescence.

Purpose

• To screen for HIV in high-risk patients.
• To screen donated blood for HIV

Patient preparation

• Explain to the patient that this test detects HIV infection.
• Provide adequate counseling about the reasons for performing the test, which is usually requested by the patient's doctor.
• If the patient has questions about his condition, be sure to provide full and accurate information.
• Tell the patient that the test requires a blood sample and who will perform the venipuncture and when.
• Reassure him that although he may experience transient discomfort from the needle puncture and the tourniquet, collecting the sample takes less than 3 minutes.

Procedure and posttest care

• Perform a venipuncture, and collect the sample in a 10-ml red-top barrier rube. Barrier tubes help prevent contamination when pouring the serum in the laboratory.
• If a hematoma develops at the venipuncture site, apply warm soaks.
• Keep test results confidential.
• When the patient receives the results, give him another opportunity to ask questions.
• Encourage the patient with positive screening tests to seek medical followup care, even if he's asymptomatic.
• Tell him to report early signs of AIDS, such as fever, weight loss, axillary or inguinal lymphadenopathy, rash, and persistent cough or diarrhea. Women should also report gynecologic symptoms.
• Tell the patient to assume that he can transmit AIDS to others until conclusively proved otherwise. To prevent possible contagion, advise him about safe sex precautions.
• Instruct him not to share razors, toothbrushes, or utensils (which may be contaminated with blood) and to clean such items with household bleach diluted 1:10 in water.
• Advise against donating blood, tissues, or an organ.
• Warn the patient to inform his doctor and dentist about his condition so that they can take proper precautions.

Precautions

• Observe standard precautions when drawing a blood sample.
• Use gloves, properly dispose of needles, and use blood-fluid precaution labels on tubes, as necessary.

Normal findings

Test results are normally negative. A positive result, indicating the presence of antibodies, necessitates further investigation.

Abnormal findings

The test detects previous exposure to the virus. However, it doesn't identify patients who have been exposed to the virus but haven't yet made antibodies. Most patients with AIDS have antibodies to HIV. A positive test for the HIV antibody can't determine whether a patient harbors actively replicating virus or when the patient will manifest signs and symptoms of AIDS.

Many apparently healthy people have been exposed to HIV and have circulating antibodies. The test results for such people aren't false-positives. Furthermore, patients in the later stages of AIDS may exhibit no detectable antibody in their sera because they can no longer mount an antibody response.

Interfering factors

• Sample taken less than 12 weeks after exposure (possible false-negative because of absence of antibodies)