A 41-year-old woman on antiretroviral therapy has had a falling CD4 count despite adherence counseling. According to standard guidelines, primary prophylaxis against disseminated Mycobacterium avium complex infection with azithromycin should begin when her CD4 count falls below:

• A 200 cells/μL
• B 150 cells/μL
• C 100 cells/μL
• D 50 cells/μL ✓

Explanation

Disseminated MAC prophylaxis with a macrolide such as azithromycin or clarithromycin is indicated once the CD4 count drops below 50 cells/μL. The 200 cells/μL threshold applies to Pneumocystis jirovecii prophylaxis with cotrimoxazole, and below 100 cells/μL to Toxoplasma gondii prophylaxis in seropositive patients. MAC disease itself typically presents at counts under 50, hence prophylaxis starts there.

Reference: Harrison's Principles of Internal Medicine, 21st ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.