Alere HIV Combo – Rapid Test

• in vitro
• Qualitative immunoassay
• 4th generation Rapid Test
• Detection of antibodies (Ab) to HIV-1 and HIV-2
• Detection of free HIV-1 p24 antigen (Ag)
• As it detects p24 antigens, it may identify HIV infection earlier than antibody-only tests

The multiplication of the HIV in the infected cells leads to cell rupture and thus the release of HIV virus particles, which are first detected in the form of HIV RNA and next in the form of HIV antigen. This is followed by production of specific antibodies to either HIV-1 or HIV-2. The HIV antigen may become undetectable at this time because of the formation of antibody-antigen complexes. Alere HIV Combo can only detect free p24 antigens.

Test Procedure

• Rapid and easy-to-use
• Lateral flow assay
• 50 μL of sample applied to a sample pad
• 1 drop of Chaser Buffer applied to sample pad
• Sample diffuses along the strip
• Results for HIV-1 p24 antigen and HIV-1 and HIV-2 antibodies
• Control window
• Results read in designated windows
• The small strip format is suitable for use with whole blood, serum, or plasma samples
• Results in 20-40 minutes

Test Results

• Control and Ab bars – Antibody reactive
• Control and Ag bars – Antigen p24 reactive
• Control, Ab and Ag bars – Antibody and Antigen p24 reactive
• Only Control bar – Non-reactive
• No Control bar – Test invalid

How the Test Works

• A specimen is added to the sample pad.
• The specimen mixes with biotinylated anti-p24 antibodies and selenium colloid-conjugates coated with recombinant HIV-1, HIV-2 and HIV-1 group O antigens, synthetic HIV-2 peptide and anti p24 mouse monoclonal antibody.
• This mixture continues to migrate through the solid phase to the immobilized recombinant HIV-1/HIV-1 group O antigens and synthetic HIV-1/HIV-2 peptides at the Antibody (Ab) window, immobilized avidin at the Antigen (Ag) window.
• If antibodies to HIV-1 and/or HIV-2 are present in the specimen, the antibodies bind to the selenium colloid-conjugates coated with recombinant HIV-1, HIV-2 and HIV-1 group O antigens and synthetic HIV-2 peptide and to the immobilized recombinant HIV-1/HIV-1 group O antigens and synthetic HIV-1/HIV-2 peptides, forming one red bar at the Ab window site.
• If antibodies to HIV-1 and HIV-2 are absent, the selenium colloid-conjugates flow past the Ab window and no red bar is formed at the Ab window site.
• If free HIV-1 p24 antigen is present in the specimen, the antigen binds to the biotinylated anti-p24 antibodies and the selenium colloid-conjugate coated with anti p24 mouse monoclonal antibody. This complex binds to the immobilized avidin forming a red bar at the Ag window site.
• If HIV-1 p24 antigen is not present, both the biotinylated anti-p24 antibodies and selenium colloid conjugate flow past the Ag window and no red bar is formed at the Ag window site.
• To ensure assay validity, a procedural control bar is incorporated in the assay device at the Control window.

Test Limitations

• No test provides absolute assurance that a specimen does not contain low levels of HIV-1 p24 antigen and/or
  antibodies to HIV-1 and HIV-2 such as those present at a very early stage or late stage of HIV infection.
• Alere HIV Combo is designed to detect antibodies to HIV-1 and/or HIV-2 and free HIV-1 p24 antigen, in human serum, plasma and capillary and venous whole blood specimens. Other body fluids or pooled specimens should not be used.
• The intensity of the Ab and Ag bars does not necessarily correlate to the titer of antibody and antigen in the specimen.
• The absence of Ag bar may occur when all p24 antigen is bound by antibodies. When high levels of antibodies against the p24 antigen are present in the blood after seroconversion, the antibodies tend to bind to the antigens, forming immunocomplexes. Alere HIV Combo detects only non-immunocomplexed (free) antigens; it does not detect immunocomplexed (bound) antigens.
• HIV-infected persons taking antiretroviral medication have been shown to produce false negative results when tested by rapid diagnostic tests.
• Infants born to HIV-infected mothers may carry maternal antibodies and will test antibody positive until eighteen months of age, which may not necessarily indicate the true infection status of the new born. The use of HIV- 1 p24 antigen testing to exclude infection in neonates (up to around eighteen months) is not recommended by CDC, because of poor sensitivity, especially in the presence of HIV antibody. Definitive diagnosis of HIV infection in early infancy requires other assays, including HIV nucleic acid test or viral culture.

More Information

Alere.com – Alere HIV Combo