## Clinical Context This patient has **virological failure** (detectable viral load >50 copies/mL after 6 months of ART) with severe immunosuppression (CD4 45 cells/μL). The cause is likely **poor adherence** (patient-reported), but **drug resistance** must be excluded before switching regimens. ## Definition of ART Failure **Key Point:** Virological failure is defined as: - Viral load >1000 copies/mL after 12 weeks of ART, OR - Viral load >50 copies/mL after 6 months of ART (confirmed on repeat testing) This patient meets criteria for virological failure at 6 months. ## Management Algorithm for Virological Failure ```mermaid flowchart TD A[Virological Failure<br/>VL >50 copies/mL at 6 months]:::outcome --> B{Assess Adherence}:::decision B -->|Poor adherence<br/>No resistance likely| C[Reinforce adherence<br/>Manage side effects<br/>Continue current ART]:::action B -->|Good adherence OR<br/>Uncertain| D[Perform HIV Resistance<br/>Testing/Genotyping]:::action D --> E{Resistance<br/>Detected?}:::decision E -->|Yes| F[Switch to Second-line ART<br/>PI-based or Integrase inhibitor]:::action E -->|No| G[Investigate other causes<br/>Poor absorption, drug interactions]:::action C --> H[Repeat VL at 4 weeks]:::action F --> I[Ensure OI Prophylaxis<br/>CD4 <50: MAC, CMV, toxo]:::action G --> I ``` ## Rationale for Correct Answer 1. **Resistance testing is mandatory** before switching ART — efavirenz resistance is common with poor adherence, but must be confirmed 2. **Adherence assessment** is critical — if poor adherence is the only issue, switching regimens will fail 3. **OI prophylaxis** must be optimized (CD4 45 requires MAC prophylaxis with azithromycin, CMV/toxo monitoring) 4. **Genotyping guides second-line selection** — if NNRTI resistance is present, switch to PI or integrase inhibitor-based regimen **High-Yield:** The sequence is: 1. Confirm virological failure (repeat VL) 2. Assess adherence 3. Perform genotyping/resistance testing 4. Switch regimen only if resistance is confirmed 5. Reinforce adherence and manage side effects **Clinical Pearl:** Switching ART without resistance testing in a patient with poor adherence often leads to **cross-resistance** and failure of second-line therapy. Efavirenz resistance (K103N mutation) is common with non-adherence and confers NNRTI class resistance. ## OI Prophylaxis at CD4 <50 | Organism | Prophylaxis | Start CD4 | |---|---|---| | *Mycobacterium avium* complex (MAC) | Azithromycin 1200 mg weekly | <50 | | *Cytomegalovirus* (CMV) | Valganciclovir (if CD4 <10 or CMV disease) | <10 | | *Toxoplasma gondii* | TMP-SMX (if CD4 <100) | <100 | | *Cryptococcus neoformans* | Fluconazole 200 mg daily | <50 | [cite:Harrison 21e Ch 197; NACO Guidelines on ART Failure (2023)]
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