The Western Blot test
The western blot test uses the general western blot procedure. A slab of gel with high voltage speed is taken and the proteins contained in the HIV infected cells are opened. The separated proteins are transferred to another plate and a procedure similar to ELISA is performed. The patient's diluted serum is poured over the plate and the HIV antibodies bind to certain proteins on the plate while others are washed away. The enzyme linked antibodies detect the presence of bound antibody. With this procedure, the proteins are separated and it is possible to see exactly to which HIV proteins the patients have antibodies. The test is considered positive if the antibodies to several major HIV proteins are present. Normally a combination of ELISA and Western blot tests are employed for diagnosing HIV infection. Blood donors are also screened with these tests.
Herpes Blood Test
Blood tests to diagnose the presence of herpes virus antibodies can be done even if the patient does not have any visible symptoms. The standard available tests are not recommended since they are not very accurate. There is a potential for false positive results. A type specific virus culture will give an accurate result only when the sores have not healed. Herpes Simplex Virus (HSV-1) and HSV-2 are the most common viruses diagnosed using type-specific blood tests. There are three methods available to diagnose herpes - Cell Culture, Antigen test and Pap Smear test.
Herpes Western Blot Test: A more sensitive test than the viral culture is the Gold Standard test known as PCR DNA test. This test also known as Herpes Western Blot test, which is rated as an accurate test to identify DNA for viral particles which easily differentiates the two types, viz. type-1 and type-2. This test can be carried out safely during pregnancy. A wide range of antibodies that respond against many herpes simplex virus proteins are tested in Western Blot test.
BIO-KIT or POCKit TEST: Recently, a more accurate POCKit type-specific test has been approved by FDA (Food and Drug Administration) to diagnose herpes simplex virus-2. A doctor's office can do this Point Of Care (POCKit) test and provide results in just 10 minutes. This new test is cost-effective and less time consuming. A positive HSV-2 test result confirms genital infection. Sensitivity in this test is around 96% accurate. Using this test during pregnancy is not approved by FDA.
ELISA ,Immunoblot and IgG type specific Elisa are the other three tests carried out to diagnose HSV-1 & HSV-2 types with the sensitivity ranging from 96% - 100%. Blood drawn from the patient's arm is sent to local labs and the results are available in a fortnight.
ELISA is an abbreviation for 'enzyme-linked immunosorbent assay'. ELISA tests are relatively accurate tests, highly sensitive and specific. They compare favorably with other methods used to detect substances in the body such as Radio immune assay (RIA) tests. ELISA tests have an added advantage in that there is no need for radioisotopes or costly radiation counter. An HIV ELISA test is also called HIV enzyme immunoassay (EIA). It is the first and basic test to determine if an individual is positive for a selected pathogen such as HIV. The test is performed in a plastic plate of 8 cm x 12 cm which contains 8 x 12 matrix of 96 wells, each of which is about 1 cm high and 0.7 cm in diameter.
A patient's serum contains certain antibodies. If the patient is HIV positive, then the serum will contain antibodies to HIV. Those antibodies will bind to the HIV antigens on the plate. Sometimes, even in some individuals not infected with HIV antibodies, positive result is given in HIV ELISA. This is called false positive. One reason for false positive is that in women who have had multiple pregnancies, may possess the antibodies directed against human leukocyte antigens (HLA) which are present in host cells used to propagate HIV. As HIV buds from the surface of the host cell, it incorporates some of the host cell HLA into its envelope. False negatives can also occur during the window between infection and an antibody response to the virus called seroconversion. A person will be retested if the serum gives positive result. If the ELISA retests are also positive, then the patient will be retested by western blot analysis.
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Bibliography / Reference
Collection of Pages - Last revised Date: December 10, 2019