Testing of HLA-B*57:01 is recommended prior to the initiation of this anti-retroviral agent
## **Core Concept**
The question pertains to the pharmacogenomics of antiretroviral therapy, specifically the association between a particular genetic marker, HLA-B*57:01, and an increased risk of a severe adverse reaction to a specific antiretroviral drug. This genetic marker is a variant of the human leukocyte antigen (HLA) gene.
## **Why the Correct Answer is Right**
The correct answer, Abacavir, is a nucleoside reverse transcriptase inhibitor (NRTI) used in the treatment of HIV/AIDS. The initiation of Abacavir is associated with a significant risk of developing a hypersensitivity reaction (HSR) in individuals who are HLA-B*57:01 positive. This reaction can be severe and life-threatening. The mechanism involves an immune-mediated response that is more likely to occur in patients with the HLA-B*57:01 allele. Therefore, testing for HLA-B*57:01 is recommended before starting Abacavir to prevent this adverse reaction.
## **Why Each Wrong Option is Incorrect**
- **Option A:** Zidovudine is another NRTI but is not associated with HLA-B*57:01 testing. Its primary side effect is bone marrow suppression leading to anemia and neutropenia.
- **Option B:** Ritonavir is a protease inhibitor used in combination with other medications to treat HIV/AIDS. It works by inhibiting the protease enzyme and does not have a known association with HLA-B*57:01 testing.
- **Option D:** Efavirenz is a non-nucleoside reverse transcriptase inhibitor (NNRTI) and does not require HLA-B*57:01 testing prior to initiation. Its common side effects include neuropsychiatric symptoms and rash.
## **Clinical Pearl / High-Yield Fact**
A crucial point to remember is that screening for HLA-B*57:01 is specifically recommended before initiating Abacavir therapy. This genetic test can help prevent Abacavir hypersensitivity reaction, which is a significant concern in the management of HIV patients. The test is particularly recommended in populations with a higher prevalence of the HLA-B*57:01 allele, such as individuals of European, North American, and Australian descent.
## **Correct Answer:** C. Abacavir