Resistance testing before initiation of antiretroviral therapy

Newly diagnosed treatment naïve HIV-positive individuals
from the HIV-CAUSAL Collaboration (Canadian and European
cohorts) were included in a study comparing two different
strategies: Testing for transmitted drug resistance (TDR)
within 3 months of baseline versus no TDR testing. Participants
in the study were included from 2006 to 2015. The probability
of 5-year virological suppression and the risks of AIDS
or death were compared. Of 25,672 individuals, 67 % had TDR
performed. Of these, 6 % had intermediate or high level TDR
to any antiretroviral drug. Resistance mutations to nevirapine
and efavirenz were the most commonly found mutations. There
was only a marginal difference in the estimated probability of
achieving viral suppression (<50 copies) after 5 years with 77 %
versus 74 % with or without TDR. There was no difference in
the incidence of death or development of AIDS.

Ref; Lodi et al. J Acquir Immune Defic Syndr 2019;82:314-320

Comment: In this large study there was no obvious clinical
benefit associated with TDR. Current guidelines recommend
initial therapy with an integrase containing regimen. As resistance
to integrase inhibitors, at least so far, is very rare it is
even less likely that TDR improves the rate of virological success
and it is common practice to initiate therapy before TDR
results are available. It is unclear how often initial therapy is
changed after TDR results become available. TDR is recommended
in high income countries and even without obvious
clinical benefits it is still important with continued surveillance
of resistance development.