Pneumocystis jiroveci pneumonia prophylaxis in HIV patients is indicated when CD4 count falls below what threshold?

• A. 200 cells/mm3
• B. 350 cells/mm3
• C. 500 cells/mm3
• D. 100 cells/mm3

Answer: (A)

Prophylaxis against Pneumocystis jirovecii pneumonia is indicated when the CD4 count drops below 200 cells per cubic millimeter. This level marks a sharp increase in risk for PCP as immune function declines, making preventive therapy important. The standard preventive treatment is trimethoprim-sulfamethoxazole, which greatly reduces PCP incidence; alternatives exist for those with sulfa allergies. Prophylaxis is typically continued until the CD4 count rises above 200 cells/mm3 for several months on effective antiretroviral therapy, at which point it can sometimes be stopped. Using a higher threshold would miss at-risk patients, while a lower threshold would delay needed protection.