Several patient characteristics have been associated with decreased regimen persistence in the extant literature [5,16-18], among them, indirect markers of advanced HIV at ART initiation (high viral loads, low CD4 counts, low weight) [24,25], non-adherence risk factors (younger age, depression, substance abuse) [25,26] and barriers to access to care (lack of medical coverage, incarceration, female gender, MSM, racial/ethnic minorities) [24,27]. This evidence concerns the gene CD4 and substance abuse.