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Category: Clinical Microbiology
Human Immunodeficiency Viruses*, Page 1 of 2
< Previous page | Next page > /docserver/preview/fulltext/10.1128/9781555817381/9781555817381.ch82-1.gif /docserver/preview/fulltext/10.1128/9781555817381/9781555817381.ch82-2.gifAbstract:
HIV is the etiologic agent of AIDS. HIV virions are enveloped positive-strand RNA retroviruses and are classified based on their degree of phylogenetic relatedness into types (HIV-1 and HIV-2), groups, subtypes, sub-subtypes, and recombinant forms. Approximately 75 million people worldwide have become infected with HIV. In the United States, the CDC estimates that 1.1 million persons are living with HIV. Previously, diagnosis was most often made by detection of antibody against HIV. HIV infection can now be expeditiously and more accurately identified during its highly infectious acute phase using a diagnostic algorithm. The algorithm employs an initial HIV-1/2 antibody/p24 antigen combination immunoassay followed by an antibody assay that differentiates HIV-1 from HIV-2 and, if necessary, a nucleic acid test to identify HIV RNA before antibodies develop. Chemiluminescent immunoassays that allow rapid processing on random-access analyzers are now available. Single-use rapid point-of-care antibody and antibody/p24 antigen combination assays that can be used with finger-stick whole blood or with oral fluids facilitate testing outside traditional laboratories. Qualitative DNA and RNA assays can diagnose acute HIV infection before seroconversion and also in infants born to HIV-infected mothers, in whom antibody tests are unreliable because of maternal antibody reactivity. Effective antiretroviral therapy delays progression of HIV disease, improves survival, and reduces infectiousness. Genotypic and phenotypic resistance assays guide the selection of antiretroviral regimens, and quantitative viral load assays that can detect fewer than 50 viral copies per ml are useful for prognosis and for monitoring response to therapy.
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Schematic representation of a mature HIV virion showing the localization of viral proteins. doi:10.1128/9781555817381.ch82.f1
Schematic representation of a mature HIV virion showing the localization of viral proteins. doi:10.1128/9781555817381.ch82.f1
Time course of appearance of laboratory markers for HIV-1 infection. Units for vertical axis not noted because their magnitude differs for RNA, p24 antigen, and antibody. Adapted data from reference 90 and updated with data from references 29 , 97 , and 107 . doi:10.1128/9781555817381.ch82.f2
Time course of appearance of laboratory markers for HIV-1 infection. Units for vertical axis not noted because their magnitude differs for RNA, p24 antigen, and antibody. Adapted data from reference 90 and updated with data from references 29 , 97 , and 107 . doi:10.1128/9781555817381.ch82.f2
Diagnostic HIV testing algorithm showing sequence of follow-up testing. doi:10.1128/9781555817381.ch82.f3
Diagnostic HIV testing algorithm showing sequence of follow-up testing. doi:10.1128/9781555817381.ch82.f3
Major HIV proteins of diagnostic significance
Major HIV proteins of diagnostic significance
HIV infection stage, based on age-specific CD4+ T-lymphocyte count or CD4+ T-lymphocyte percentage of total lymphocytes
HIV infection stage, based on age-specific CD4+ T-lymphocyte count or CD4+ T-lymphocyte percentage of total lymphocytes
FDA-approved viral load assays and specimen requirements
FDA-approved viral load assays and specimen requirements
FDA-approved conventional laboratory HIV serologic tests
FDA-approved conventional laboratory HIV serologic tests
FDA-approved rapid and point-of-care HIV tests
FDA-approved rapid and point-of-care HIV tests
HIV-1 resistance and tropism assays
HIV-1 resistance and tropism assays