Low-level HIV viremia is associated with greater overall mortality, as well as a greater likelihood of developing severe non-AIDS-defining conditions, according to a Swedish study of 6,956 participants who started antiretroviral treatment between 1996 and 2017 that was published in Clinical Infectious Diseases. The research adds to a relatively mixed set of study results over the past several years attempting to tease out the clinical risks of detectable HIV viral loads below 1,000 copies/mL.
By the end of the study period, 60% of participants were virally suppressed (defined as a viral load consistently below 50 copies/mL), 9% had low-level viremia (defined as two or more consecutive viral load results between 50 and 999 copies/mL), and 31% were not virally suppressed (defined as at least one viral load of 1,000 copies/mL or greater).
In an adjusted analysis of the study data, participants with low-level viremia were 2.2 times as likely to die within the study period than participants with fully suppressed HIV. (By comparison, participants with a viral load of 1,000 or higher were 7.7 times as likely to die than virally suppressed participants.) These results did not significantly differ by antiretroviral regimen. Given the long study period, most participants changed HIV regimens at some point, but the results also held among those who did not switch antiretrovirals.
The risk of serious non-AIDS events short of death was greater among those at the higher end of the low-level viremia bracket (200-999 copies/mL) compared to virally suppressed participants. No significant relationship was seen among people with low-level viremia between 50 and 199 copies/mL.
The study authors posited that the relatively lengthy time span of their study may account for the discrepancy between their findings and those of prior large studies that did not find a significant relationship between low-level viremia and mortality risk.
They noted, however, that one limitation in their findings was a lack of information on smoking habits and socio-economic backgrounds, which could influence mortality rates. Participants starting antiretroviral treatment in the early years of the study period also took different, possibly more toxic, drugs than those who began treatment later.
Nonetheless, “these findings add to mounting evidence that [low-level viremia] is associated with worse clinical outcomes,” study authors concluded.