CD4 and tuberculosis: However, a positive IGRA test in HIV-infected persons with relatively intact immunity (CD4 cell count > 350 cells/μL and HIV viral load < 100,000 copies/mL) can improve the estimation for the risk of incident active TB, and increases the sensitivity from 52.9% (HIV viral load and CD4 approach alone) to 76.5% (HIV viral load and CD4 approach augmented with IGRA).