American Board of Internal Medicine (ABIM) Certification Practice Exam

At what CD4 cell count should concern for toxoplasmosis arise?

1. 200/µL

2. 150/µL

3. 100/µL

4. 50/µL

The correct answer is: 100/µL

Toxoplasmosis is a significant opportunistic infection associated with HIV/AIDS, particularly as the disease progresses and immune function declines. The risk of developing toxoplasmosis increases as the CD4 cell count lowers. Generally, a CD4 count of less than 100 cells/µL is established as the threshold at which individuals are considered to be at high risk for this infection. At this CD4 count level, the immune system is significantly compromised, allowing for reactivation of latent Toxoplasma gondii infections or exposure to new infections, particularly from environmental sources or undercooked meat. Therefore, monitoring the CD4 count is critical in managing patients with HIV to ensure early detection and preventive measures against opportunistic infections, including toxoplasmosis. When the CD4 count drops below 100 cells/µL, clinicians typically recommend initiating prophylactic treatment with medications such as trimethoprim-sulfamethoxazole to prevent the onset of toxoplasmosis, which would not be the case at higher CD4 counts (such as 200/µL or 150/µL) where the immune response remains more robust.