CD4 and bacterial infectious disease: In addition to the need of CD4 testing for treatment eligibility and monitoring response to treatment, CD4+ T-cell testing is used to guide initiation of co-trimoxazole prophylaxis in patients with a CD4+ T-cell count ≤200 cells/μL or ≤350 cells/μL to prevent co-infections such as Pneumocystis carinii, toxoplasmosis and bacterial infections [2], and the initiation of fluconazole prophylaxis in patients with a CD4+ T-cell count ≤100 cells/μL to prevent cryptococcal disease [3].