Which laboratory value is NOT used in the monitoring or staging of HIV infection?

Correct answer: C. Haemoglobin A1c

• A. The CD4+ count is the central staging parameter in HIV. Below 200 cells/µL defines AIDS and marks the threshold for prophylaxis against Pneumocystis jirovecii pneumonia.
• B. Helper T-lymphocyte count is simply another name for the CD4+ count — the same central monitoring parameter.
• C. CORRECT. Haemoglobin A1c reflects average glycaemia over roughly the preceding 2 to 3 months — the lifespan of a red cell — and is a diabetes marker with no role in HIV staging. (Ironically, HbA1c can be falsely LOW in HIV patients on certain antiretrovirals because of altered red cell turnover, but that is a caveat about interpreting it, not a use for it.)
• D. The total white cell count is followed in HIV because leukopenia is common, and because it is the denominator from which the absolute CD4 count is derived (WBC × % lymphocytes × % CD4).

Note: The two numbers that drive HIV management are CD4 count (immune competence, and therefore infection risk) and viral load (treatment response). For dental care, a CD4 above 200 with a suppressed viral load generally means routine treatment without modification.