AIDS Diagnosis Based on Lymphocyte Threshold

Steps:

• Recall AIDS diagnosis occurs when lymphocyte count drops below 200 cells/mm³.
• Analyze the graph: lymphocyte count starts high post-infection and declines over time.
• Identify the point where the curve crosses below 200 cells/mm³.
• Determine the corresponding time: 10 years after infection.

Why D is correct:

• Lymphocyte count falls below 200 cells/mm³ at 10 years, fulfilling the CDC diagnostic criterion for AIDS in HIV patients.

Why the others are wrong:

• A: At 0 years, count is normal (above 1000 cells/mm³), no AIDS.
• B: At 3 years, count remains above 500 cells/mm³, not diagnostic.
• C: At 7 years, count is still above 200 cells/mm³, insufficient for diagnosis.

Final answer: D