American Board of Internal Medicine (ABIM) Certification Practice Exam

Why is the Western blot test no longer recommended for HIV diagnosis?

1. It is too expensive

2. It does not detect recent infections

3. It has low specificity

4. It is difficult to administer

The correct answer is: It does not detect recent infections

The Western blot test is no longer recommended for HIV diagnosis primarily because it does not effectively detect recent infections. This limitation is particularly significant given the urgency of identifying and treating individuals who have recently contracted HIV, as early diagnosis can lead to timely intervention, reducing the risk of transmission and improving health outcomes. In the context of HIV diagnosis, the test also suffers from timing issues; antibodies may take several weeks to develop, meaning that a person with a recent acute infection might receive a negative result despite being infectious. Modern diagnostic approaches, particularly fourth-generation tests, which can simultaneously detect both HIV antibodies and the p24 antigen, provide a more comprehensive picture, enabling earlier detection of infection, including acute HIV. While factors like cost, specificity, and administration might play a role in testing strategy, the inability of the Western blot to catch recent infections is the more critical flaw that has led to its decreased use in clinical practice for HIV diagnosis. This shift emphasizes the importance of utilizing tests that are more effective in early detection of HIV, thereby aligning with public health goals to manage and control the infection.