Cohorts, trials, and evidence: expanding our confidence in guidelines for antiretroviral resistance testing

Prevalence of drug-resistant HIV type 1 at the time of initiation of antiretroviral therapy in Portland, Oregon

The presence of transmitted drug-resistant HIV-1 (TDR) at the time of antiretroviral therapy (ART) initiation is associated with failure to achieve viral load suppression. Rates of TDR in ART-naive patients have been reported from various parts of the world through ongoing national, regional, and global evaluations; however, surveillance of TDR in Portland, Oregon has not been previously described. We describe the prevalence of TDR in patients in the Portland area who have recently entered care. Genotypic data were obtained from plasma specimens collected between 2003 and 2009 from 165 recently identified HIV-1-positive, ART-naive adults in care at the Multnomah County Health Department. Median time from diagnosis to first genotype was 2.7 months. Mutations associated with TDR were observed in 33 (20.0%) patients. Mutations associated with resistance to nucleoside reverse transcriptase (RT) inhibitors (NRTI), nonnucleoside RT inhibitors (NNRTI), and protease inhibitors (PI) were found in 15 (9.1%), 17 (10.3%), and 5 (3.0%) patients, respectively (p=0.013 for NNRTI vs. PI, and 0.035 for NRTI vs. PI, Fisher exact test). Dual class resistance was observed in four (2.4%) patients. Predominant RT mutations included M41L, T215C or S, and K103N. The prevalence of HIV-1 with NRTI resistance-associated mutations increased from 2006 to 2008-2009 (p=0.004) based on date of diagnosis. These data indicate relatively high rates of drug resistance present prior to ART initiation among patients in the Portland area, and support continued surveillance of local trends of TDR to inform optimal individual treatment strategies and public health decisions.