Quantification of HIV-1 RNA (Human Immunodeficiency Virus Type 1) in the blood of patients infected with the virus can be used as a complementary test when serological tests are positive. Quantification of HIV-1 is also useful when other confirmatory tests are unclear or cannot be interpreted accurately. Immediate identification of the virus is also useful for differentiating HIV infection in newborns due to the passive transmission of HIV antibodies from the HIV-positive mother.
Quantification of HIV-1 RNA measures viral load. Viral load determination is used:
- Before starting antiviral therapy
- To detect the resistance of the virus to drugs during anti-HIV therapy
- To determine the patient's non-compliance with drug antiviral therapy
- To monitor the progress of the disease, whether in or out of medication
- To determine the need to initiate antiretroviral therapy
- To determine the course of the disease, because it is more sensitive than any other test, including the measurement of CD4 T-cells
- As a determinant of patient survival
HIV-1 viral load is determined by quantifying the genetic material of the virus in the patient's blood. There are several different laboratory methods for measuring HIV viral load. It is important to use the same method to monitor the course of a patient's disease. The most common method is reverse-transcriptase real-time polymerase chain reaction (RT-PCR).
In general, it is recommended that the initial viral load be determined in two measurements 2 to 4 weeks after HIV infection. Follow-up may be repeated by testing every 3 to 4 months, in combination with determining CD4 lymphocyte counts. Both tests provide data used to determine when antiviral therapy will begin. Determination of viral load can be repeated every 4 to 6 weeks after initiation or change of antiviral therapy. Usually, antiretroviral treatment is continued until the viral load of HIV is less than 500 copies/mL. It is important to note that a "zero" test result does not mean that no virus remains in the blood after treatment. Practically it means that the viral load has fallen below the detection limit of the method. Possible causes of a "zero" result include very low HIV viral load (e.g., from 1 to 199 copies/mL), very recent HIV infection (ie, less than 3 weeks after infection), or absence of HIV infection (i.e. false-positive result of serological tests). A significant (more than threefold) increase in viral load should re-evaluate treatment.
This method can quantify HIV-1, with a sensitivity of 200 copies/mL. The measurement range is 5x102 to 1x108 copies/ml.
Important Note
Laboratory test results are the most important parameter for the diagnosis and monitoring of all pathological conditions. 70%-80% of diagnostic decisions are based on laboratory tests. The correct interpretation of laboratory results allows a doctor to distinguish "healthy" from "diseased".
Laboratory test results should not be interpreted from the numerical result of a single analysis. Test results should be interpreted in relation to each individual case and family history, clinical findings, and the results of other laboratory tests and information. Your personal physician should explain the importance of your test results.
At Diagnostiki Athinon we answer any questions you may have about the test you perform in our laboratory and we contact your doctor to get the best possible medical care.
