25621 HIV-1 & HIV-2 Ab, Confirmation/Diff (HVDIP)

Acquired Immune Deficiency Syndrome (AIDS)
Anti-HIV
Anti-HIV-1/-2
Anti-HIV-1/-2 Differentiation
HIV Types 1 and 2 Antibodies
HIV-1/-2
HIV-1/-2 Ab
HIV-1/-2 Antibodies
HIV-1/-2 Antibody Differentiation
HIV Antibody Differentiation
Human Immunodeficiency Virus (HIV)

AIDS is caused by 2 known types of HIV. HIV type 1 (HIV-1) is found in patients with AIDS, AIDS-related complex, and 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 a HIV-1/-2 antigen and/or antibody screening test, which may be performed by various FDA-approved assay methods, including rapid HIV antibody tests, enzyme immunoassays, 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 according to assay manufacturers' instructions for use.

Negative results for both HIV-1 and HIV-2 antibodies usually indicate the absence of HIV-1 and HIV-2 infection. However, in patients with reactive initial combined HIV-1/-2 antigen and antibody test results, such negative results do not rule-out acute or early HIV infection. If acute or early HIV infection is suspected, detection of HIV-1 RNA (HIVDQ / HIV-1 RNA Detection and Quantification, Plasma) and/or HIV-2 DNA/RNA (FHV2Q / HIV-2 DNA/RNA Qualitative Real-Time PCR) is recommended, based on patient’s clinical and epidemiologic exposure history.

Positive HIV-1 antibody, but negative HIV-2 antibody results, indicates the presence of HIV-1 infection. Together with reactive initial combined HIV-1/-2 antigen and antibody test results, individuals with such results are presumed to have HIV-1 infection. Verification of a first-time positive test result is recommended for the diagnosis of HIV-1 infection. Additional testing with a newly submitted plasma specimen for HIV-1 RNA (HIVDQ) is recommended to verify and confirm the diagnosis of HIV-1 infection prior to initiating antiretroviral treatment.

Positive HIV-1 antibody, but indeterminate HIV-2 antibody results, indicates the presence of HIV-1 infection, with probable cross-reactivity of HIV-1 antibodies with HIV-2 antigens on the assay strip. Verification of a first-time positive test result is recommended for the diagnosis of HIV-1 infection. Submit a plasma specimen for detection of HIV-1 RNA (HIVDQ). However, such result patterns may rarely indicate early HIV-2 infection (ie, HIV-2 coinfection) in HIV-1-infected individuals. For individuals at risk for HIV-2 infection (based on epidemiologic exposure history), a plasma specimen should be submitted also for HIV-2 DNA/RNA (FHV2Q).

Indeterminate HIV-1 antibody, but negative HIV-2 antibody results, suggest either very early HIV-1 infection (in individuals with risk factors) or the presence of nonspecific cross-reactivity between the patients' specimens and HIV-1 antigens on the assay strip. If patient has known risk factors for HIV-1 infection, a new specimen should be submitted for HIV-2 serologic testing (HIV2 / HIV-2 Antibody Evaluation, Serum or HIV2M / HIV-2 Antibody Screen, Serum) or HIV-2 DNA/RNA (FHV2Q).

Negative HIV-1 antibody, but indeterminate HIV-2 antibody results, suggests either very early HIV-2 infection (in individuals with risk factors) or presence of nonspecific cross-reactivity between the patients' specimens and HIV-2 antigens on the assay strip. If patient has known risk factors for HIV-2 infection (based on patient's clinical and epidemiologic history), a new specimen should be submitted for HIV-2 serologic testing (HIV2 or HIV2M) or HIV-2 DNA/RNA (FHV2Q).

Positive results for both HIV-1 and HIV-2 antibodies suggest probable the presence of HIV-1 and HIV-2 coinfection. However, such results may be rarely due to: a) HIV-1 infection with HIV-2 antibody cross-reactivity; or b) HIV-2 infection with HIV-1 antibody cross-reactivity (eg, absence of HIV-1 p24 and p31 bands). Verification of a first-time positive test result is recommended for the diagnosis of HIV infection. Based on patient's clinical and epidemiologic history, plasma specimens should be submitted for detection of HIV-1 RNA (HIVDQ) and/or HIV-2 DNA/RNA (FHV2Q).

Indeterminate results for both HIV-1 and HIV-2 antibodies indicate either very early HIV infection (in individuals with risk factors) or the presence of nonspecific cross-reactivity between the patients' specimens and HIV antigens on the assay strip. Nonspecific cross-reactivity may be due to recent non-HIV infections, hypergammaglobulinemic states, connective tissue disorders, or pregnancy (alloantibodies). For individuals at risk for HIV infection, plasma specimens should be submitted for detection of HIV-1 RNA (HIVDQ) and/or HIV-2 DNA/RNA (FHV2Q), depending on the epidemiologic exposure history.

Negative HIV-1 antibody, but positive HIV-2 antibody results, indicates the presence of HIV-2 infection. Together with a reactive initial HIV-1/-2 antigen and antibody screening test results, individuals with such results are presumed to have HIV-2 infection. Additional testing with a newly submitted plasma specimen for HIV-2 DNA/RNA (FHV2Q) is recommended to verify and confirm the diagnosis of HIV-2 infection prior to initiating antiretroviral treatment.

Reactive HIV-1 antibody, but positive HIV-2 antibody results, usually indicates the presence of HIV-2 infection with HIV-1 antibody cross-reactivity (eg, presence of only HIV-1 gp41 and/or gp160 band). However, such results may be rarely due to HIV-1 and HIV-2 coinfection. Verification of a first-time positive test result is recommended for the diagnosis of HIV-2 infection, by submitting a new specimen for HIV-2 serologic testing (HIV2 or HIV2M) or a plasma specimen for HIV-2 DNA/RNA (FHV2Q). If the patient is at risk for HIV-1 infection (based on patient's clinical and epidemiologic history), a plasma specimen should be submitted also for detection of HIV-1 RNA (HIVDQ).

Indeterminate HIV-1 antibody, but positive HIV-2 antibody results, indicates the presence of HIV-2 infection, with probable cross-reactivity of HIV-2 antibodies with HIV-1 antigens on the assay strip. Verification of a first-time positive test result is recommended for the diagnosis of HIV-2 infection, by submitting a plasma specimen for (FHV2Q). However, such result patterns may rarely indicate early HIV-1 infection (ie, HIV-1 coinfection) in HIV-2-infected individuals. For individuals at risk for HIV-1 infection, (based on epidemiologic exposure history), plasma specimen should be submitted also for detection of HIV-1 RNA (HIVDQ).