26484 HIV-1 and HIV-2 Antigen and Antibody Diagnostic Evaluation, Plasma (HIVDX)

​​.​Acquired Immune Deficiency Syndrome (AIDS), Anti-HIV, Anti-HIV-1/-2, HIV Types 1 and 2 Antibodies, HIV-1/-2, HIV-1/-2 Ab, HIV-1/-2 Ag/Ab, HIV-1/-2 Antibodies, HIV-1/-2 Antigen, HIV combo, Human Immunodeficiency Virus (HIV)

​This test begins with HIV-1/-2 antigen and antibody screen by chemiluminescence immunoassay. If the screen result is reactive, then HIV-1/-2 antibody confirmation/differentiation test by immunochromatographic method is performed at an additional charge.

If the following result types are obtained from the HIV-1/-2 confirmation/differentiation test, HIV-1/HIV-2 RNA detection will be performed at an additional charge:

-Negative for both HIV-1 Ab and HIV-2 Ab

-Indeterminate for HIV-1 Ab but negative for HIV-2 Ab

-Negative for HIV-1 Ab but indeterminate for HIV-2 Ab

-Indeterminate for both HIV-1 Ab and HIV-2 Ab

-Positive for both HIV-1 Ab and HIV-2 Ab

If the following result types are obtained from the HIV-1/-2 confirmation/differentiation, HIV-1 RNA detection and quantification will be performed at an additional charge:

-Positive for HIV-1 Ab and negative for HIV-2 Ab

-Positive for HIV-1 Ab and indeterminate for HIV-2 Ab

​Diagnosing HIV-1 and/or HIV-2 infection in symptomatic patients more than 2 years old

Follow-up testing of individuals with reactive rapid HIV test results

This test is not offered as a screening or confirmatory test for blood donor specimens.

1. Centrifuge blood collection tube per collection tube manufacturer's instructions (eg, centrifuge and aliquot within 2 hours of collection for BD Vacutainer tubes).

2. Aliquot plasma into a plastic vial.

​Reactive result of this assay does not differentiate among reactivity with HIV-1 p24 antigen, HIV-1 antibody, and HIV-2 antibody.

A reactive screening test result is not diagnostic for HIV infection and should be considered preliminary.

The positive predictive value of a reactive screening test result is highly dependent on the prevalence of HIV infection in the population tested. The lower the prevalence of HIV infection, the lower the positive predictive value and higher the false-positive rate of the test. Diagnosis of HIV infection must be based on positive results of the supplemental or confirmatory serologic or molecular tests.

Recipients of experimental HIV-1 vaccines may have false-reactive HIV antibody test results due to the presence of vaccine-induced, HIV-1-specific antibodies without actual HIV infection.

Negative serologic or molecular HIV screening test results should be evaluated with caution in patients with clinical symptoms and/or a history of high-risk behavior for HIV infection. Repeat testing in 1 to 2 months is recommended in these at-risk individuals.

Assay performance characteristics have not been established for the following specimen characteristics:

-Grossly hemolyzed (hemoglobin level of >500 mg/dL)

-Grossly lipemic (triolein level of >1250 mg/dL)

-Grossly icteric (total bilirubin level of >20 mg/dL)

-Heat-inactivated specimens

-Cadaveric specimens

-Presence of particulate matter

AIDS is caused by 2 known types of HIV. HIV type 1 (HIV-1) is found in patients with AIDS or  AIDS-related complex and in asymptomatic infected individuals at high risk for AIDS. The virus is transmitted by sexual contact, by exposure to infected blood or blood products, or from an infected mother to her fetus or infant. HIV type 2 (HIV-2) infection is endemic only in West Africa, and it has been identified in individuals who had sexual relations with individuals from that geographic region. HIV-2 is similar to HIV-1 in viral morphology, overall genomic structure, and its ability to cause AIDS.

Antibodies against HIV-1 and HIV-2 are usually not detectable until 6 to 12 weeks following exposure and are almost always detectable by 12 months. They may fall to undetectable levels (ie, seroreversion) in the terminal stage of AIDS when the patient's immune system is severely depressed.

Routine serologic screening of patients at risk for HIV-1 or HIV-2 infection usually begins with an HIV-1/-2 antigen and/or antibody screening test, which may be performed by various US Food and Drug Administration approved assay methods, including rapid HIV antibody tests, enzyme immunoassays, and chemiluminescent immunoassays. In testing algorithms that begin with these methods, supplemental or confirmatory testing should be requested only for specimens that are repeatedly reactive by these methods.

Negative HIV-1/-2 antigen and antibody screening test results usually indicate the absence of HIV-1 and HIV-2 infection. However, such negative results do not rule-out acute HIV infection. If acute HIV-1 infection is suspected, detection of HIV-1 RNA (HIVQN / HIV-1 RNA Detection and Quantification, Plasma) or HIV-1 DNA and RNA (HIVP / HIV-1 DNA and RNA Qualitative Detection by PCR, Plasma) is recommended.

Reactive HIV-1/-2 antigen and antibody screening test results suggest the presence of HIV-1 and/or HIV-2 infection, but it is not diagnostic for HIV infection and should be considered preliminary. A reactive result does not differentiate among reactivity with HIV-1 p24 antigen, HIV-1 antibody, and HIV-2 antibody. Diagnosis of HIV infection must be based on results of supplemental tests, such as HIV antibody confirmation/differentiation test (automatically reflexed on all samples with reactive screen test results at an additional charge).

All initially positive supplemental or confirmatory HIV test results (by serologic or molecular test methods) should be verified by submitting a second plasma specimen for repeat testing. Such positive HIV test results are required under laws in many states in the United States to be reported to the departments of health of the respective states where the patients reside.