Component Description The estimated prevalence of human immunodeficiency virus (HIV) infection in the United States population is an important measure of the extent of the medical and financial burden the nation faces because of this virus. The current NHANES and HIV antibody data from NHANES III (1988–94) serve as a baseline for monitoring the changes in the epidemic over time in the general population of the United States.
Participants aged 18–49 years who did not refuse the HIV antibody test.
Blood specimens were processed, stored, and shipped to the Division of AIDS, STD, and TB, National Center for HIV, STD, and TB Prevention, National Centers for Disease Control and Prevention. Detailed specimen collection and processing instructions are discussed in the LPM. Read the General Documentation of Laboratory Data file for detailed data processing and editing protocols. The analytical methods are described in the Description of the Laboratory Methodology section.
HIV antibody blood assay test results:
All specimens were tested using the Synthetic Peptide Enzyme Immunoassay (EIA) (Genetic Systems HIV-1/HIV-2 Peptide EIA) for the detection of antibody to human immunodeficiency virus type 1 or type 2 (HIV-1 or HIV-2) or both (Bio-Rad Laboratories, Redmond, WA). Any specimen that reacted in an initial test was retested in duplicate with the Genetic Systems HIV-1/HIV-2 Peptide EIA. Initially, reactive specimens that were reactive in either one or both duplicates from the repeat testing are referred to as “repeatedly reactive”. These repeatedly reactive specimens were then tested with a more specific test, the Cambridge Biotech HIV-1 Western Blot Kit (Calypte Biomedical Corporation, Rockville, MD).
The combination of electrophoretic separation of complex mixtures of antigens with the highly sensitive immunoblotting technique has been useful in characterizing the antigenic profile of HIV-1 and describing the immune response to this virus in exposed or infected persons.
The Cambridge Biotech HIV-1 Western Blot Kit, when used as directed, will detect antibodies to HIV-1 when present in human serum or plasma. The position of bands on the nitrocellulose strips allows this antibody reactivity to be associated with specific viral antigens.
The Cambridge Biotech HIV-1 Western Blot Kit is manufactured by Calypte Corporation from HIV-I propagated in an H9/HTLV-IIIb T lymphocyte cell line. The partially purified virus is inactivated by treatment with psoralen, ultraviolet light, and detergent disruption. Specific HIV-1 proteins are fractionated according to molecular weight by electrophoresis on a polyacrylamide slab gel in the presence of sodium dodecyl sulfate (SDS).
The separated HIV-1 proteins are elecrotransferred from gel to a nitrocellulose membrane, which is then washed, blocked (to minimize nonspecific immunoglobulin binding), and packaged. Individual nitrocellulose strips are incubated with serum or plasma specimens, or controls. During incubation, if HIV-1 antibodies are present in the specimen, they will bind to the viral antigens bound to the nitrocellulose strips. The strips are washed again to remove unbound material.
Visualization of the human immunoglobulins specifically bound to HIV-1 proteins is accomplished in situ by using a series of reactions with goat anti-human IgG conjugated with biotin, avidin conjugated with horseradish peroxidase (HRP), and the HRP substrate 4-chloro-1-naphthol. If antibodies to any of the major HIV-1 antigens are present in the specimen in sufficient concentration, bands corresponding to the position of one or more of the following HIV-1 proteins (p) or glycoprotiens (gp) will be seen on the nitrocellulose strip: p17, p24, p31, gp41, p51, p66, gp120, gp160 (number refers to apparent molecular mass in kilodaltons).
There have been no changes from the previous two years to the equipment, lab methods, or lab site. However, no CD4/8 counts were measured in 2007-2008.
A detailed description of the laboratory method used can be found on the NHANES website.
Read the General Documentation of Laboratory Data file for detailed data processing and editing protocols. The analytical methods are described in the Analytic Notes for Data Users section below. Read the Analytic Notes section below to understand how the variable (LBDHI) was derived.
he NHANES quality assurance and quality control (QA/QC) protocols meet the 1988 Clinical Laboratory Improvement Act mandates. Detailed quality control and quality assurance instructions are discussed in the NHANES Laboratory/Medical Technologists Procedures Manual (LPM). Read the General Documentation of Laboratory Data file for detailed QA/QC protocols. A detailed description of the quality assurance and quality control procedures can be found on the NHANES website.
Analytic Notes The serum specimens were first tested by enzyme immunoassay (EIA) and confirmed by Western blot (WB). If the EIA was repeatedly negative, the HIV antibody result was coded as negative. If the EIA was positive and the WB was positive, the result was coded as positive. If the EIA was positive or indeterminate but the WB was negative, the result was coded as negative. If the EIA was positive or indeterminate but the WB was indeterminate, the result was coded as indeterminate.
CD4+ counts were not measured in 2007-2008.
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