Type of test
Blood
Normal findings
No resistant HIV
Test explanation and related physiology
There are several factors that affect the success of HIV antiviral medications, including patient compliance, access to adequate care, optimal dosing, and drug pharmacology issues. Another significant factor that determines a patient’s response to antiviral HIV drugs is the percentage of an HIV viral population that is resistant to the drugs that are administered. HIV resistance to therapy develops in 78% of patients. HIV genotyping is able to detect changes in the viral genome that are associated with drug resistance and is particularly able to predict HIV-1 resistance to protease and reverse-transcriptase inhibitor antiretroviral drugs.
HIV genotyping is particularly useful when failure of the most active antiviral therapy is suspected from decreasing CD4 counts. HIV genotyping can also be performed in conjunction with HIV drug sensitivity testing. HIV sensitivity testing estimates the ability of a cloned copy of the patient’s virus to replicate in a cell culture in the presence of a particular antiviral drug. This same testing can help determine the amount of drug needed to inhibit viral replication.
Interfering factors
• If the plasma HIV-1 RNA viral load is less than 1000 copies per mL of plasma, genotyping may be inaccurate.
• Minor HIV-1 populations that are less than approximately 20% of the total population may not be identified.
Procedure and patient care
• See inside front cover for Routine Blood Testing.
• Fasting: no
• Blood tube commonly used: lavender or pink
* Instruct the patient to observe the venipuncture site for infection. Patients with AIDS are immunocompromised and susceptible to infection.
Abnormal findings
Drug resistance
