HIV 1/2 Testing Algorithm
HTLV-III Antibodies, HIV Antibodies, HIV Ag/Ab Test, HIV Combo, HIV 1/2 Screen, HIV Screen , EPIC: LAB5766, SOFT: HIV4G
Specimen Collection Criteria
Collect: One Gold-top SST tube. (Minimum Whole Blood: 4.0 mL)
Contact the Laboratory for acceptability of other tube types.
Physician Office/Drawsite Specimen Preparation
Let SST specimens clot 30-60 minutes then immediately centrifuge to separate serum from cells. Refrigerate (2-8°C or 36-46°F) the centrifuged SST tube within two hours of collection. (Min: 2.0 mL)
Preparation for Courier Transport
Transport: Centrifuged SST tube, refrigerated (2-8°C or 36-46°F). (Min: 2.0 mL)
- Heat inactivated serum.
- Severely lipemic or hemolyzed specimens.
- Specimens that have obvious bacterial contamination.
- Red-top tubes with serum not separated from cells within two hours of collection.
Sunday - Saturday, 24 hours a day.
Negative results available within 24 hours.
Positive results for HIV-1 Antibodies available within 24 hours.
If sendout testing for HIV-1 RNA or additional testing for HIV-2 is necessary, results may take an additional week. See algorithm below.
- A negative test result does not rule out the possibility of exposure to, or infection with, HIV.
- An initial positive screen will be followed by confirmation testing (see algorithm below) and an interpretative report summarizing results of all tests will be issued.
The initial screen is a 4th generation assay that detects both HIV-1 p24 antigen and antibodies to HIV-1 (groups M and O) and HIV-2. The new screen will detect acute HIV infection, on average 7 to 10 days earlier than the previously used antibody-only screen.
Positive screen confirmation antibody testing to distinguish HIV-1 from HIV-2 will be performed in-house within 24 hours of initial testing. Western blots (currently a send-out test) will no longer be ordered. Rarely, additional molecular-based confirmation testing for HIV-1 and/or HIV-2 will be performed (Send Out) as delineated in the algorithm below. All test results will be included in a single report with a final interpretation.
HIV-1 IgG is first detectable 3-12 weeks after infection in nearly all cases except neonates. Once established, HIV antibody levels usually persist throughout the lifetime of the patient. The presence of antibody does not imply immunity to the virus but rather, that the patient is assumed to be infected, and infectious. (3) Little is known about the antibody response to HIV-2 infection. The response is presumed to be similar to HIV-1. (3)
Primary HIV infections are symptomatic in 50-70% of patients. These patients present with a variety of symptoms including Influenza-like or mononucleosis-like illness to more severe neurological symptoms. These symptoms may persist for a few days or up to two months. Rapid progression to AIDS is seen in patients that experience a longer acute illness. Most patients however, remain asymptomatic for 1 to greater than 10 years before the clinical symptoms of AIDS present. (2)
- CDC. 2006. The global HIV/AIDS pandemic, 2006. MMWR. 55: 841-844.
- CDC. 2006. Epidemiology of HIV/AIDS---United States. 1981-2005. MMWR. 55: 589-592.
- Schusbach, J. 2003. Human Immunodeficiency viruses. Manual of Clinical Microbiology, 8th edition. P.R. Murray et al. (eds). ASM Press. Washington, D.C., pp. 1253-1281.
Initial Screen: 87389.
If screen is positive: 86701, 86702.
Further confirmation testing (if necessary): 87535, 87538.
EPIC: LAB5766, SOFT: HIV4G