Different studies were able to identify a number of factors associated with failure to PI/r-MT, including nadir and baseline CD4+ count, duration of viral suppression, previous failure to ART, HCV co-infection, PI in the baseline cART, residual viremia levels at time of switch, hemoglobin levels, age, VL at cART initiation, gender, mode of HIV transmission [26–37]. Here, CD4 is linked to coinfection.