Which CD4 count defines AIDS in an HIV-infected patient?

Which CD4 count defines AIDS in an HIV-infected patient?

• A. < 200 cells/µL
• B. < 500 cells/µL
• C. < 800 cells/µL
• D. < 50 cells/µL

Answer: (A)

The main concept here is that AIDS diagnosis hinges on a marked decline in CD4 T cells, signaling severe immune system compromise. In HIV infection, the virus destroys helper T cells, and when the CD4 count falls below 200 cells per microliter, the risk of life-threatening opportunistic infections and certain cancers rises dramatically. This threshold is used clinically and on exams to define AIDS in the absence of an AIDS-defining illness. Normal CD4 counts are roughly 500–1500 cells/µL, so 200 is well below normal and represents significant immunosuppression. It’s also important to note that AIDS can be diagnosed if an AIDS-defining illness occurs regardless of the CD4 count, but the CD4 criterion of below 200 is the standard laboratory definition. Counts such as less than 500 or less than 800 are not AIDS-defining thresholds; they indicate varying degrees of immunosuppression but do not meet the criterion for AIDS. A count around 50 is extremely low and signals severe immunodeficiency, but it is not the designated cutoff for AIDS.

The main concept here is that AIDS diagnosis hinges on a marked decline in CD4 T cells, signaling severe immune system compromise. In HIV infection, the virus destroys helper T cells, and when the CD4 count falls below 200 cells per microliter, the risk of life-threatening opportunistic infections and certain cancers rises dramatically. This threshold is used clinically and on exams to define AIDS in the absence of an AIDS-defining illness. Normal CD4 counts are roughly 500–1500 cells/µL, so 200 is well below normal and represents significant immunosuppression. It’s also important to note that AIDS can be diagnosed if an AIDS-defining illness occurs regardless of the CD4 count, but the CD4 criterion of below 200 is the standard laboratory definition.

Counts such as less than 500 or less than 800 are not AIDS-defining thresholds; they indicate varying degrees of immunosuppression but do not meet the criterion for AIDS. A count around 50 is extremely low and signals severe immunodeficiency, but it is not the designated cutoff for AIDS.