Type of test Blood
Normal findings
Undetected
Test explanation and related physiology
Quantification of HIV RNA in the blood of patients infected with HIV can be used after immunoassay tests are positive. Quantification is also helpful when confirmatory tests are indeterminate or cannot be accurately interpreted. Direct viral testing is helpful in differentiating newborn HIV infection from passive transmission of HIV antibodies from an HIV-infective mother. Finally, HIV RNA quantification testing determines HIV viral load. Determining viral load is used:
• to establish a baseline viral load before initiating anti HIV-1 drug therapy
• to identify HIV-1 drug resistance while on anti-HIV therapy
• to identify noncompliance with anti–HIV-1 drug therapy
• to monitor HIV-1 disease progression
• to recommend the initiation of antiretroviral treatment (Table 1)
• to indicate the course of the disease because it is more accurate than any other test, including CD4 T-cell counts
• as a determinant of patient survival (Table 2)
HIV viral load is most accurately determined by quantifying the amount of genetic material of the virus in the blood. In general, it is recommended to determine the baseline viral load by obtaining two measurements 2 to 4 weeks apart after HIV infection. Monitoring may continue with testing every 3 to 4 months in conjunction with CD4 counts. Both tests provide data used to determine when to start antiviral treatment. The viral load test can be repeated every 4 to 6 weeks after starting or changing antiviral therapy. Usually, antiviral treatment is continued until the HIV viral load is less than 500 copies/mL. It is important to recognize that a nondetectable result does not mean that no virus is left in the blood after treatment; it means that the viral load has fallen below the limit of detection by the test. A significant (> threefold) rise of viral load should warrant re-evaluation of therapy.
Table1. Recommendations for antiretroviral therapy based on viral load and CD4 count
Table2. Using the viral load to predict disease course
Interfering factors
• Incorrect handling and processing of the specimen can cause inconsistent results. • Recent vaccinations may affect viral levels.
• Concurrent infections can cause inconsistent results.
• Variable compliance to therapy may alter test results.
Procedure and patient care
• See inside front cover for Routine Blood Testing.
• Fasting: no
• Blood tube commonly used: lavender
• Specimens are often sent to a central laboratory.
* Instruct the patient to observe the venipuncture site for infection.
* Patients with AIDS are immunocompromised and susceptible to infection.
* Encourage the patient to discuss his or her concerns regarding the prognostic information from test results.
• Do not give test results over the phone. Increasing viral load results can have devastating consequences.
• Because test results vary according to the laboratory test method, it is important to use the same laboratory method for monitoring the course of the disease.
• Viral loads are usually repeated after starting or changing antiviral therapy.
Abnormal findings
HIV infection
