Emerging Infectious Diseases by Beltz Lisa A

Author:Beltz, Lisa A. [Beltz, Lisa A.]
Language: eng
Format: mobi, epub
Publisher: John Wiley & Sons, Inc.
Published: 2011-03-02T21:00:00+00:00

Diagnosis and Detection

Several types of tests have been developed to permit detection of HIV. These tests are used diagnostically and to screen the blood supply in order to remove any contaminated units. Some of these tests rely on immunological detection. ELISA is used to identify either antibodies to HIV gp120 or viral antigens themselves in the blood. Due to the length of time required to mount an adaptive immune response that produces antibodies, such tests may not detect the presence of HIV in blood until six months after infection. Western blot assays test for the presence of viral proteins and may be used in a confirmatory manner. The polymerase chain reaction detects HIV genes. The latter two tests allow detection of the virus much sooner after infection than immunological tests and often scan for the presence of more than one HIV gene product to avoid false-positive results. Thanks to the use of these tests, the number of infections via the blood supply in developed countries is now extremely low.

Molecular detection of HIV load in plasma has been used to predict disease severity. Individuals with a low steady-state number of viral copies in the plasma tend to progress to severe disease more slowly than those with high numbers of plasma viruses. The ratio of CD4:CD8 T lymphocytes in the blood is also used as a marker of disease progression: this ratio drops as disease progresses.

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