a test before starting or changing antiviral treatment.observation of patients without antiviral treatment.confirmation of a newly diagnosed HIV infection.vague HIV antibody test results in a patient at high risk of infection.there is a reasonable suspicion of HIV, infection or the patient is showing signs of a viral infection.The most common reasons for Plasma Viral Load (PVL) are: NASBA – Nucleic Acid Sequence-Based Amplification.PCR assay – Polymerase Chain Reaction Assay.Plasma Viral Load is a set of tests that quantitatively detect the presence of viral RNA in a patient's plasma. Graph showing HIV copies and CD4 counts in a human over the course of a treatment-naive HIV infection In the case of an indeterminate western blot result, it is time to test the amount of viral RNA present in the plasma: Plasma Viral Load. For clients with a low probability of infection, we can consider the test as negative, but also with the possibility of further monitoring. If the patient is at high risk for HIV infection, it is recommended that they be monitored for at least 6 months. Some healthy people may produce antibodies that cross-react with specific HIV-1 peptides or recombinant antigens for no apparent reason. Performing a test in the late phase of HIV infection may result in failure to capture antibodies to the virus's core proteins. Testing in the diagnostic window will cause some antibodies to be not detectable in the sample. The indeterminate result can have many causes. However, re-testing is recommended for patients at high risk of infection, as with the ELISA the patient may be infected recently and tested in the diagnostic window. The error may be due to sample swapping, contamination of negative samples with positive samples, or antibodies to HLA antigenům antigens in the virus lysate used in the assay, and misinterpretation of electrophoretic bands from the sample.Ī negative result is considered to be no infection and the patient is, therefore, HIV negative. The specificity of the western blot is 97.8%, which means that more than 2% of the tests are false positive. If only some antibodies are present that do not meet the criteria of the positive test, the test result is marked as indeterminate.Ī positive Western blot in combination with a positive ELISA test already means the almost certain presence of HIV, the patient is HIV positive and treatment can start. The presence of certain groups of antibodies is always evaluated. Western blot detects the presence of antibodies against virus proteins: core-proteins (p17, p24, p55), polymerases (p31, p51, p66) a envelope-proteins (gp41, gp120, gp160). It is advantageous to perform tests with samples taken by the same method and evaluated in the same laboratory. If the results of both tests are different (positive and negative), it is tested again. If the second ELISA test is positive again, further testing (western blot) is performed for a high probability of infection. The causes are the same as for a false-negative test, and false-positive results can also be obtained with intravenous drug use, vaccination ( hepatitis, rabies,…) or HIV vaccination as part of the research. If the test is positive, the ELISA is repeated because, of course, the test may be false-positive. The ELISA may also be false negative in cases of autoimmune disease, renal failure, hemodialysis, cystic fibrosis, multiple pregnancies or transfusions, and liver disease. The diagnostic window can last up to 12 weeks (depending on the ELISA type). Although the infection is present in the body, detectable amounts of antibodies have not yet begun to form. However, there may be situations where the patient has recently become infected, resulting in a window period. If the test is negative, there is no reason to suspect HIV infection and the patient is considered healthy. Therefore, the ELISA is used in most cases as the first test in case of suspected HIV infection. The specificity and sensitivity of this test is more than 99%. ELISA is one of the methods for detecting the patient's production of antibodies to the virus. The basis of testing for the presence of HIV in the body is the detection of antibodies in serum or other body fluids. In case of problems with the diagnosis or with the patient, a whole range of other tests is prepared to help confirm or refute the HIV infection. The basis is an ELISA (Enzyme-linked Immunosorbent Assay) test supplemented by western blot. Standard aids diagnosis Ī single multi-test algorithm is used to diagnose human immunodeficiency virus (HIV) infection causing acquired immune deficiency syndrome (AIDS).
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