Type of test Blood or fluid analysis (saliva)

Normal findings

 No evidence of HIV antigen or antibodies

 Test explanation and related physiology

 There are two active types of human immunodeficiency viruses, types 1 and 2. HIV-1 is the most prevalent type within the United States and Western Europe, whereas HIV-2 is mostly limited to Western African nations. Immunoassay testing identifies antibodies developed as a result of HIV-1 or HIV-2 infections. Virologic tests identify RNA (or DNA) specific to HIV. Virologic tests can identify HIV infection in the first 11 days after infection. Serologic immunoassay tests can identify HIV infection only after about 3 weeks. This 3-week time period is called the seroconversion window.

Immunoassay testing for HIV is divided into screening tests and confirmatory tests (Table 1).

Table1. Serologic testing for HIV

In the past, serologic screening of patients suspected of having HIV-1 or HIV-2 infection usually began with an HIV antibody “screening test.” If positive, a confirmatory test was required to make the diagnosis of HIV infection. HIV serologic qualitative screening tests (for HIV-1 and HIV-2) were used to screen high- and low-risk individuals (Box 1) or for donor blood products. Because these rapid screening qualitative antibody immunoassays do not detect viral antigens, they could not detect infection in its earliest stage (before antibodies are formed). Because some persons who undergo HIV testing do not return to learn their test results, “point-of-service” rapid HIV antibody immunoassay screening testing in which results can be available in less than 1 hour is available. This is particularly helpful in urgent or emergent care points of service where HIV transmission could occur from blood or body fluid contamination. Furthermore, rapid antibody testing is helpful during labor in women whose HIV status is unknown. Point-of-care home kits are also available. Confirmatory tests for HIV-1 and HIV-2 antibodies include the Western blot assay and the indirect immunofluorescence assay (IFA). See screening recommendations (Table 2). The U.S Preventive Services Task Force (USPSTF) recommends that clinicians screen for HIV infection in adolescents and adults aged 15 to 65 years. Younger adolescents and older adults who are at increased risk of infection should also be screened. Furthermore, all pregnant persons, including those who present in labor or at delivery, whose HIV status is unknown should be screened. Repeat screening is reasonable for persons known to be at increased risk of HIV infection (Box 1).

Table2. Centers for Disease Control and Prevention HIV screening recommendations

Box1. Risk factors for HIV infection

The p24 direct serologic antigen assay detects the viral protein p24 in the peripheral blood of HIV-infected individuals in which it exists either as a free (core) antigen or complexed to anti-p24 antibodies. The p24 antigen may be detectable as early as 16 days after infection. The p24 antigen test can be used to assess the antiviral activity of anti-HIV therapies. The p24 antigen test can also be used to differentiate active neonatal HIV infection from passive HIV antibody present from the mother’s blood. It is also used to detect HIV infection before antibody seroconversion, to detect HIV in donor blood, and to monitor therapy.

The use of oral fluids for serologic HIV testing is as an alternative to serum testing. These HIV-1 antibody tests use oral mucosal transudate (OMT), a serum-derived fluid that enters saliva from the gingival crevice and across oral mucosal surfaces. Another alternative to blood testing is urine testing for HIV. Only a spot urine collection is required. Testing urine for HIV antibodies is valuable, especially when venipuncture is inconvenient, difficult, or unacceptable. Insurance companies also commonly use it. It is important to note that all urine HIV tests are detecting antibodies and not the HIV particles. Urine does not contain the virus and is not a body fluid capable of infecting others. HIV antigen/antibody (Ag/Ab) combination assays are now available that can detect HIV infection on average 5 to 7 days earlier than assays that only detect antibodies.

Interfering factors

 • False-positive results can occur in patients who have autoimmune disease, lymphoproliferative disease, leukemia, lymphoma, syphilis, or alcoholism.

• False-positive results can occur in noninfected pregnant woman.

 • HIV-2 infection can cause positive HIV-1/HIV-2 screening antibody test and an indeterminate WB HIV-1 confirmatory test.

 • False-negative results can occur in the early incubation stage or end stage of AIDS.

Procedure and patient care

• See inside front cover for Routine Blood Testing.

• Fasting: no

 • Blood tube commonly used: red

• Obtain an informed consent if required by the institution for all “opt in” testing.

 • The blood is often sent to an outside laboratory for testing, although rapid antibody testing kits are becoming increasingly available in hospital laboratories and even in homes.

 • If the patient wishes to remain anonymous, use a number with the patient’s name; be sure to record it accurately.

• Note that if the serologic test is reactive (i.e., test result is positive twice consecutively), the Western blot test is performed on the same blood sample.

* Instruct the patient to observe the venipuncture site for infection. Patients with AIDS are immunocompromised and susceptible to infection.

 • Follow the institution’s policy regarding test result reporting. Do not give results over the telephone. Remember that positive results may have devastating consequences, including loss of job, insurance, relationships, and housing.

* Explain to the patient that a positive Western blot test merely implies HIV infection. It does not mean that the patient has clinical AIDS. Not all patients with positive antibodies will acquire the disease.

* Encourage patients who test positive to inform their sexual contacts so that they can be tested. Most new cases of HIV infection are transmitted from patients who are unaware of their HIV status.

*  Inform the patient that subsequent sexual contact will put new partners at high risk for contracting AIDS.

 Abnormal findings

 Increased levels

 -AIDS

-HIV infection

مواضيع ذات صلة

Nucleic Acid –Based Tests

human chorionic gonadotropin (hCG, Pregnancy tests, hCG beta subunit)

homocysteine (Hcy)

HIV RNA quantification (HIV viral load)

Molecules involved in Lipoprotein metabolism

Lipoproteins

Retinol Binding Protein

Direct Visualization Of The Organism

Direct Detection Methods for Bacillus and Similar Organisms

HIV drug resistance testing (HIV genotype)

herpes simplex (Herpesvirus types 1 and 2, Herpes simplex virus types 1 and 2 [HSV 1, HSV 2], Herpes genitalis)

hepatitis virus studies