Anti-retroviral therapy is started when CD4 count is less than
**Core Concept**
Anti-retroviral therapy (ART) is initiated in patients with HIV infection to suppress viral replication and prevent progression to AIDS. The decision to start ART is based on the patient's CD4 count, clinical symptoms, and viral load. A low CD4 count indicates compromised immune function and increased risk of opportunistic infections.
**Why the Correct Answer is Right**
The World Health Organization (WHO) and various clinical guidelines recommend initiating ART in patients with a CD4 count below 350 cells/μL. This is because a CD4 count below 350 cells/μL is associated with an increased risk of opportunistic infections, such as tuberculosis, pneumonia, and toxoplasmosis. The CD4 count is a critical indicator of the patient's immune status, and a low count suggests that the patient's immune system is compromised.
**Why Each Wrong Option is Incorrect**
**Option A:** A CD4 count of 400 cells/μL is generally considered normal, and ART is not typically initiated at this level.
**Option B:** A CD4 count of 250 cells/μL may indicate a need for ART, but it is not the specific threshold recommended by WHO guidelines.
**Option C:** A CD4 count of 500 cells/μL is above the normal range and does not typically indicate a need for ART.
**Clinical Pearl / High-Yield Fact**
It's essential to remember that the decision to start ART is based on a combination of factors, including CD4 count, clinical symptoms, and viral load. A low CD4 count is a critical indicator of immune compromise, and ART should be initiated promptly to prevent progression to AIDS.
**Correct Answer:** C. 350