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HIV-1&2 Antibody
MessageObtain patient consent per local medical center policy prior to ordering test.
If the HIV result is Reactive the Lab will add on a reflex HIV-1/2 AB DIFF test that is performed at the WestHaven VA.
If the HIV result is Reactive the Lab will add on a reflex HIV-1/2 AB DIFF test that is performed at the WestHaven VA.
Test Code
HIV-1&2 AB
Alias/See Also
Chemistry
Preferred Specimen
Gold Top Tube
Plasma Separator Tube
Plasma Separator Tube
Minimum Volume
2 mL
Other Acceptable Specimens
Light Green Top Tube
Transport Temperature
Refrigerate
Specimen Stability
Room temperature: 3 days
Refrigerated (2-8°C): 7 days
Separate and freeze at -20°C or colder if not tested within 7 days.
Max freeze/thaw cycles: 5
Refrigerated (2-8°C): 7 days
Separate and freeze at -20°C or colder if not tested within 7 days.
Max freeze/thaw cycles: 5
Methodology
This assay is a two-step immunoassay for the qualitative detection of HIV-1 p24 antigen and antibodies to HIV-1 (group M and group O), and HIV-2 in human serum or plasma using chemiluminescent microparticle immunoassay (CMIA) technology.
Sample, paramagnetic microparticles, assay diluent, and wash buffer are combined and incubated. The HIV-1 p24 antigen and HIV-1/HIV-2 antibodies present in the sample bind to the HIV-1/HIV-2 antigen and HIV-1 p24 monoclonal (mouse) antibody coated microparticles. The mixture is washed. Acridinium-labeled conjugate is added to create a reaction mixture and incubated. The bound HIV-1 p24 antigen and HIV-1/HIV-2 antibodies bind to the acridinium-labeled conjugates. Following another wash cycle, Pre-Trigger and Trigger solutions are added.
The resulting chemiluminescent reaction is measured as relative light units (RLUs). There is a relationship between the amount of HIV antigen and antibodies in the sample and the RLUs detected by the system optics.
The presence or absence of HIV-1 p24 antigen or HIV-1/HIV-2 antibodies in the sample is determined by comparing the chemiluminescent RLU in the reaction to the cutoff RLU determined from an active calibration.
Specimens with signal to cutoff (S/CO) values greater than or equal to 1.00 are considered reactive for HIV-1 p24 antigen or HIV-1/ HIV-2 antibodies. Specimens with S/CO values less than 1.00 are considered nonreactive for HIV-1 p24 antigen and HIV-1/ HIV-2 antibodies.
Specimens that are initially reactive in the Alinity i HIV Ag/Ab Combo assay should be retested in duplicate. Repeat reactivity is highly predictive of the presence of HIV-1 p24 antigen and/or HIV-1/HIV-2 antibodies. However, as with all immunoassays, the Alinity i HIV Ag/Ab Combo assay may yield nonspecific reactions due to other causes, particularly when testing in low prevalence populations. A repeatedly reactive specimen should be investigated further with supplemental confirmatory HIV-specific tests, such as immunoblots, antigen tests, and HIV nucleic acid tests. Supplemental testing of repeatedly reactive specimens obtained from individuals with HIV infection usually confirms the presence of HIV antibodies, HIV antigen, or HIV nucleic acid. A full differential diagnostic work-up for the diagnosis of AIDS and AIDS-related conditions includes an examination of the patient’s immune status and a clinical history.
Setup Schedule
M-F
Report Available
TAT 1 - 4 days
Reference Range
Non-Reactive
Clinical Significance
Acquired immunodeficiency syndrome (AIDS) is caused by two types of human immunodeficiency viruses, collectively designated HIV.1, 2, 3, 4 HIV is transmitted by sexual contact, exposure to blood or blood products, and prenatal or perinatal infection of a fetus or newborn.5 Antibodies against HIV are nearly always detected in AIDS patients and HIV-infected asymptomatic individuals.5, 6
Phylogenetic analysis classifies HIV type 1 (HIV-1) into groups M (major), N (non-M, non-O), O (outlier), and P.7, 8, 9, 10 HIV-1 group M is composed of genetic subtypes (A-D, F-H, J, and K) and circulating recombinant forms (CRFs).8, 11 Group M viruses have spread throughout the world to cause the global AIDS pandemic. However, the geographic distribution and regional predominance of HIV-1 subtypes and CRFs vary.12 HIV-1 subtype B is the predominant subtype in North America, South America, Europe, Japan, and Australia, although other subtypes and CRFs are present in these regions as well.12 A significant percentage of new HIV-1 infections in Europe are caused by non-B subtype strains.13, 14 All subtypes and many recombinant strains exist in Africa.12 In Asia, subtypes B and C, and CRF01_AE (formerly called subtype E) are found.12 HIV-1 groups N, O, and P are endemic to west central Africa and are relatively rare.7, 9, 10, 15, 16 However, group O infections have been identified in Europe and the USA.14, 17, 18
HIV type 2 (HIV-2) is similar to HIV-1 in its structural morphology, genomic organization, cell tropism, in vitro cytopathogenicity, transmission routes, and ability to cause AIDS.4 HIV-2 is endemic to West Africa, but HIV-2 infections have been identified in North America and Europe at a low frequency compared to HIV-1.14, 19, 20, 21
Early after infection with HIV-1, but prior to seroconversion, HIV-1 core protein, p24 antigen, may be detected in HIV-1-infected individuals.22 Alinity i 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.
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.6, 23, 24 Alinity i HIV Ag/Ab Combo 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.
Phylogenetic analysis classifies HIV type 1 (HIV-1) into groups M (major), N (non-M, non-O), O (outlier), and P.7, 8, 9, 10 HIV-1 group M is composed of genetic subtypes (A-D, F-H, J, and K) and circulating recombinant forms (CRFs).8, 11 Group M viruses have spread throughout the world to cause the global AIDS pandemic. However, the geographic distribution and regional predominance of HIV-1 subtypes and CRFs vary.12 HIV-1 subtype B is the predominant subtype in North America, South America, Europe, Japan, and Australia, although other subtypes and CRFs are present in these regions as well.12 A significant percentage of new HIV-1 infections in Europe are caused by non-B subtype strains.13, 14 All subtypes and many recombinant strains exist in Africa.12 In Asia, subtypes B and C, and CRF01_AE (formerly called subtype E) are found.12 HIV-1 groups N, O, and P are endemic to west central Africa and are relatively rare.7, 9, 10, 15, 16 However, group O infections have been identified in Europe and the USA.14, 17, 18
HIV type 2 (HIV-2) is similar to HIV-1 in its structural morphology, genomic organization, cell tropism, in vitro cytopathogenicity, transmission routes, and ability to cause AIDS.4 HIV-2 is endemic to West Africa, but HIV-2 infections have been identified in North America and Europe at a low frequency compared to HIV-1.14, 19, 20, 21
Early after infection with HIV-1, but prior to seroconversion, HIV-1 core protein, p24 antigen, may be detected in HIV-1-infected individuals.22 Alinity i 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.
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.6, 23, 24 Alinity i HIV Ag/Ab Combo 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.
Performing Laboratory
Test performed at West Roxbury Chemistry Lab
Contact: Jonathan Dryjowicz-Burek 857-203-5973
Last Updated: December 19, 2025
