From the Guidelines
Response to antiretroviral treatment (ART) should be assessed through regular viral load testing, with the goal of achieving undetectable levels (<50 copies/mL) within 24 weeks, as recommended by the 2020 International Antiviral Society-USA panel 1. The most important measure is HIV viral load, which should be tested at baseline before starting treatment, then at 4-8 weeks after initiation, and every 3-6 months thereafter. Effective treatment should reduce viral load to undetectable levels within 24 weeks, and CD4 counts should be measured at baseline and every 3-6 months during the first two years of treatment, then annually if stable and virologically suppressed. Additional blood tests include:
- Complete blood count
- Liver function tests (ALT, AST, bilirubin)
- Kidney function tests (creatinine, estimated glomerular filtration rate)
- Lipid profile
- Glucose levels to monitor for medication side effects. For patients on specific medications, specialized monitoring may be required, such as HLA-B*5701 testing before initiation of abacavir, or closer kidney function monitoring for those on tenofovir, as suggested by the guidelines 1. Treatment success is defined as sustained viral suppression with immune recovery (increasing CD4 counts), while treatment failure is indicated by persistent detectable viral load despite adherence or declining CD4 counts, and should prompt reassessment of patient adherence, consideration of repeat RNA testing, or a change in drug regimen, as recommended by the 2020 guidelines 1. These laboratory parameters are essential for ensuring the effectiveness of ART and minimizing drug toxicity, and should be monitored regularly, with adjustments made as needed to optimize treatment outcomes, in accordance with the latest recommendations 1.
From the FDA Drug Label
Virologic response was defined as a confirmed plasma HIV-1 RNA viral load less than 50 copies/mL The median increase from baseline in CD4+ cell counts was 258 cells/mm3 in the darunavir/ritonavir 800 mg/100 mg once daily arm and 263 cells/mm3 in the lopinavir/ritonavir 800 mg/200 mg per day arm Of the darunavir/ritonavir subjects with a confirmed virologic response of < 50 copies/mL at Week 48,81% remained undetectable at Week 192 versus 68% with lopinavir/ritonavir.
To assess response to anti-retroviral treatment in terms of blood tests, virologic response is defined as a confirmed plasma HIV-1 RNA viral load less than 50 copies/mL. Additionally, CD4+ cell count is used to monitor the treatment response, with an increase in CD4+ cell count indicating a positive response to treatment. The median increase from baseline in CD4+ cell counts can be used to evaluate the effectiveness of the treatment regimen. 2 2
From the Research
Assessing Response to Anti-Retroviral Treatment
To assess the response to anti-retroviral treatment in terms of blood tests, several factors need to be considered:
- CD4 cell count: This is a crucial marker for assessing the immune system's response to treatment 3, 4, 5, 6.
- Viral load: Monitoring viral load is essential for determining the effectiveness of treatment and making adjustments as needed 4, 5, 7, 6.
- HIV-1 RNA level: This test measures the amount of HIV RNA in the blood and is used to monitor the viral load 5.
Blood Tests for Monitoring Treatment Response
The following blood tests are used to monitor the response to anti-retroviral treatment:
- CD4 cell count tests: These tests measure the number of CD4 cells in the blood, which indicates the health of the immune system 3, 4, 5, 6.
- Viral load tests: These tests measure the amount of HIV RNA in the blood, which indicates the level of viral activity 4, 5, 7, 6.
- HIV-1 RNA level tests: These tests measure the amount of HIV RNA in the blood, which is used to monitor the viral load 5.
Frequency of Blood Tests
The frequency of blood tests for monitoring treatment response varies depending on the individual's condition and the treatment regimen:
- CD4 cell count tests: These tests are typically performed every 3-6 months 4, 5.
- Viral load tests: These tests are typically performed every 3-6 months, but may be performed more frequently in some cases 4, 5, 7.
- HIV-1 RNA level tests: These tests are typically performed every 3-6 months 5.
Factors Affecting Treatment Response
Several factors can affect the response to anti-retroviral treatment, including:
- Baseline CD4 cell count: Patients with lower baseline CD4 cell counts may be more likely to experience treatment failure 6.
- Baseline viral load: Patients with higher baseline viral loads may be more likely to experience treatment failure 6.
- Adherence to treatment: Adherence to the treatment regimen is critical for achieving and maintaining viral suppression 7.