According to WHO classification, what is the CD4+ T cell count threshold below which a patient with HIV is classified as having AIDS in the absence of an AIDS-defining illness?

Explanation

## WHO/CDC AIDS Classification Criteria **Key Point:** A CD4+ T cell count of <200 cells/μL is the immunological criterion for AIDS diagnosis, regardless of clinical symptoms or presence of opportunistic infections. ### CD4+ Count Thresholds in HIV Disease Progression | CD4+ Count (cells/μL) | Clinical Stage | Risk of OI | | --- | --- | --- | | >500 | Early HIV | Minimal | | 200–500 | Advanced HIV | Moderate | | <200 | AIDS | High (PCP, toxoplasmosis, cryptococcosis) | | <50 | Severe immunosuppression | CMV, MAC, cryptococcal meningitis | **High-Yield:** The CD4+ count of 200 cells/μL is a critical threshold used globally for: - Diagnosis of AIDS (even without OIs) - Initiation of PCP prophylaxis (TMP-SMX) - Timing of ART initiation in resource-limited settings - Prognostic stratification **Clinical Pearl:** A patient with HIV and a CD4+ count of 150 cells/μL meets the definition of AIDS, even if they have no opportunistic infections or AIDS-defining illnesses at that moment. **Mnemonic:** **"200 is the AIDS threshold"** — this is the single most important CD4+ cutoff in HIV management.