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1. ELISA - Enzyme Linked Immunosorbent Assay
This type of blood test is used to screen blood for transfusions as well as diagnose patients.
The latest generation of ELISA tests are 99.5% sensitive to HIV. Occasionally, the ELISA test will be positive for a patient without symptoms of AIDS from a low-risk group. Because this result is likely to be a false-positive, the ELISA must be repeated on the same sample of the patient's blood. If the second ELISA is positive, the result should be confirmed by the Western Blot test.
Getting tested earlier than 3 months may result in an unclear test result, as an infected person may not yet have developed antibodies to HIV.
2. Western Blot
The Western blot or immunoblot test is used as a reference procedure to confirm the diagnosis of AIDS. About nine different HIV-1 proteins can be detected in the blots.
When used in combination with ELISA testing, Western blot testing is 99.9% specific. It can, however, yield false negatives in patients with very early HIV infection and in those infected by HIV-2. In some patients the Western blot yields indeterminate results.
3. IFA - Immuno-Fluorescence Assay
This method is sometimes used to confirm ELISA results instead of Western blotting.
4. PCR - Polymerase Chain Reaction
This test is used to evaluate the very small number of AIDS patients with false-negative ELISA and Western blot tests.
The polymerase chain reaction (PCR) test can measure the presence of viral nucleic acids in the patient's blood even when there is no detectable antibody to HIV. This test works by amplifying the presence of HIV nucleic acids in a blood sample. Numerous copies of a gene are made by separating the two strands of DNA containing the gene segment, marking its location, using DNA polymerase to make a copy, and then continuously replicating the copies. Since the virus is continually generating new variants, PCR testing could yield a false negative in patients with these new variants.
1. ELISA - Enzyme Linked Immunosorbent Assay
This type of blood test is used to screen blood for transfusions as well as diagnose patients.
The latest generation of ELISA tests are 99.5% sensitive to HIV. Occasionally, the ELISA test will be positive for a patient without symptoms of AIDS from a low-risk group. Because this result is likely to be a false-positive, the ELISA must be repeated on the same sample of the patient's blood. If the second ELISA is positive, the result should be confirmed by the Western Blot test.
Getting tested earlier than 3 months may result in an unclear test result, as an infected person may not yet have developed antibodies to HIV.
2. Western Blot
The Western blot or immunoblot test is used as a reference procedure to confirm the diagnosis of AIDS. About nine different HIV-1 proteins can be detected in the blots.
When used in combination with ELISA testing, Western blot testing is 99.9% specific. It can, however, yield false negatives in patients with very early HIV infection and in those infected by HIV-2. In some patients the Western blot yields indeterminate results.
3. IFA - Immuno-Fluorescence Assay
This method is sometimes used to confirm ELISA results instead of Western blotting.
4. PCR - Polymerase Chain Reaction
This test is used to evaluate the very small number of AIDS patients with false-negative ELISA and Western blot tests.
The polymerase chain reaction (PCR) test can measure the presence of viral nucleic acids in the patient's blood even when there is no detectable antibody to HIV. This test works by amplifying the presence of HIV nucleic acids in a blood sample. Numerous copies of a gene are made by separating the two strands of DNA containing the gene segment, marking its location, using DNA polymerase to make a copy, and then continuously replicating the copies. Since the virus is continually generating new variants, PCR testing could yield a false negative in patients with these new variants.