Intended to be used as an aid in the diagnosis of HIV-1/HIV-2 infection, including acute or primary HIV-1 infection.  The assay may also be used as an aid in the diagnosis of HIV-1/HIV-2 infection in pediatric subjects (i.e., children as young as two years of age) and in pregnant women.

Early after infection with HIV-1, but prior to seroconversion, HIV-1 core protein, p24 antigen, may be detected in HIV-1-infected individuals.  The 4th generation ARCHITECT HIV Ag/Ab Combo uses anti-HIV-1 p24 antibodies as reagents to detect HIV-1 p24 antigen, thereby decreasing the window period and improving early detection of HIV infection.  On average, the assay should be positive by day 16 after infection.  HIV RNA appears earlier after the eclipse phase so the HIV RNA PCR will be positive on average by day 11 after infection.  The new screening test does not eliminate the need for ordering the HIV RNA test in appropriate cases.

The key immunogenic protein for serodetection of HIV infection is the viral transmembrane protein (TMP).  Antibodies against the TMP are consistently among the first to appear during seroconversion of HIV-infected individuals and remain relatively strong throughout the asymptomatic and symptomatic stages of HIV infection.  The ARCHITECT HIV Ag/Ab Combo  Assay detects antibodies to HIV-1 groups M and O, and HIV-2 through the use of five recombinant proteins and two synthetic peptides derived from native TMP sequences of HIV-1 groups M and O, and HIV-2.

An ARCHITECT HIV Ag/Ab Combo reactive result does not distinguish between the detection of HIV-1 p24 antigen, HIV-1 antibody, or HIV-2 antibody.

Specimens that are reactive in the ARCHITECT HIV Ag/Ab Combo assay are highly predictive of the presence of HIV-1 p24 antigen and/or HIV-1/HIV-2 antibodies.  However, as with all immunoassays, the ARCHITECT HIV Ag/Ab Combo assay may yield nonspecific reactions due to other causes, particularly when testing in low prevalence populations.  A supplemental differentiation assay, the BioRad Multispot HIV-1/HIV-2 Antibody is used to test all repeatedly reactive specimens as a reflex.  This supplemental/differentiation assay of repeatedly reactive specimens obtained from individuals with HIV infection usually confirms the presence of HIV antibodies.  If not, the HIV-1 VIRAL LOAD Assay is recommended along with an Infectious Diseases consult to assess a possible acute infection.  Antibody levels may be undetectable in acute stage HIV infection. In high-risk cases, repeat the testing within 1 month after initial NEGATIVE HIV antibody report. 

For individuals who test reactive for antibodies, appropriate counseling and medical evaluation should be offered.  AIDS and AIDS-related conditions are clinical syndromes and their diagnosis can only be established clinically.  Testing alone cannot be used to diagnose AIDS, even if the recommended investigation of reactive specimens suggests a high probability that the antibody to HIV-1 or HIV-2 is present.

The risk of an asymptomatic person with a repeatedly reactive serum developing AIDS or an AIDS-related condition is not known, as the course of HIV infection may vary among individual patients and may be altered by antiretroviral therapy.

Some patients with clinical AIDS test negative to antibodies due to the breakdown of their immune system.  However, most AIDS patients do have antibodies to at least a few of the HIV major proteins.

A person who has participated in an HIV vaccine study may develop antibodies to the vaccine and may or may not be infected with HIV.  Clinical correlation is indicated with appropriate counseling, medical evaluation, and possibly additional testing to decide whether a diagnosis of HIV infection is accurate.

In children younger than 2 years of age, HIV Antibody results require clinical correlation. Neither (+) or (-) results are absolutely conclusive.  Nearly all infants born to HIV-infected mothers passively acquire maternal antibody and, in some cases, will test antibody positive until age 18 months regardless of whether they are infected.  Definitive diagnosis of HIV infection in early infancy requires other assays, including HIV nucleic acid tests or viral culture. Consult Infectious Disease for assistance. 

The sensitivity of the ARCHITECT HIV Ag/Ab Combo assay in a large study of patients infected with HIV-1 was 100.00% with an exact 95% confidence interval of 99.63 to 100.00%.

The sensitivity of the ARCHITECT HIV Ag/Ab Combo assay in a smaller study of patients infected with HIV-2 was 100.00% with an exact 95% confidence interval of 98.18 to 100.00%.

The specificity of the ARCHITECT HIV Ag/Ab Combo assay in the low risk population in a large study was 99.77% with an exact 95% confidence interval of 99.62% to 99.88%.

The Clinical Microbiology Laboratory performs the BioRad Multispot HIV-1/HIV-2 differentiation assay as a reflex on all specimens positive by the Abbott Architect Assay.  Final positive or indeterminate reports are based on the results of this assay.  

The laboratory reports all reactive results to the NC State Laboratory of Public Health in accordance with state law 10A NCAC 41A.0101-Communicable Disease Control.

1.  High levels of Hepatitis C antibody in patient serum may cross react with the Architect HIV Ag/Ab Combo assay, resulting in a false positive test.

2.  Heterophilic antibodies in human serum can react with reagent immunoglobulins, interfering with in vitro immunoassays.  Patients routinely exposed to animals or to animal serum products can be prone to this interference and anomalous results may be observed.

Screening Assay/Kit Test- Rapid Vertical Flow Immunoassay

Confirmatory test- Abbott ARCHITECT HIV Antigen/Antibody Combo Assay (4th generation) immunoassay using microparticles and chemiluminescent reaction (CMIA technology) 

Includes testing by a differentiation assay at an additional charge when screening assay is repeatedly reactive. 

"Stat" testing is available in case of an emergency transplant situation. Contact Clinical Microbiology (DUKE: 684-2089, DRH: 470-5262) to request testing.

Order the Labor/Delivery HIV-1 Antibody test if "stat" testing is needed in the case of a laboring woman whose HIV status is unknown or of a newborn whose mother's HIV status is unknown.

All requests ordered on patients in the Emergency Department will be processed as "stat".