Other variables that had p-values < 0.05 in the univariate analysis, including height, chronic hepatitis B infection, nadir CD4 lymphocyte count, plasma HIV RNA load before cART, CD4 count at the time of determinations of plasma EFV C12, and concurrent ART backbone, were not significantly associated with plasma EFV C12 in the backward selection model. Here, CD4 is linked to chronic hepatitis B virus infection.