2505. Incidence of Transmitted Drug Resistance and Its Clinical Implications Between 1999 and 2018 in a Regional HIV Population

Background Baseline genotype antiretroviral resistance testing (GART) were introduced to allow better selection of antiretroviral therapy (ART), minimizing the use of less effective drugs and risk for ongoing transmission of drug-resistant virus. However, the value of baseline GART has recently been questioned due to declining incidence of TDR in the setting of improved drug tolerability profiles and effectiveness. We aimed to evaluate the long-term clinical and economic impact of TDR using a well characterized, geographically defined cohort between 1999–2018. Methods In the Southern Alberta Cohort (SAC) database we identified all (ART naïve) HIV patients, ≥16 years of age, with a baseline GART. They were classified by presence or absence of TDR. Clinical and sociodemographic data were obtained from database and chart review. All statistical analysis was performed with Stata. Results During the study 745 GART tests were done on ART naïve patients. Baseline ART resistance was documented in 78 /745 patients. TDR was to the NNRTI class in 59 (75.6%), to NRTI in 12 (15.4%) and to the PI class in 7 (8.9%) patients. Two patients had two class resistance and none had INSTI resistance. There was a significant difference in cost per year of therapy comparing the TDR and control ($17,152/year vs. $15,362/year, P ≤ 0.001). Patients with TDR had greater pill burden with 20% being on BID/TID ART regimens compared with the controls of 13% (P = 0.003). No differences in incident ART adverse events (12.8% TDR vs. 13.3% no TDR), drug interactions (1.6% vs. 1.0%) or reasons to stop or change ARVs were seen between study groups. The duration of ART on any given drug class was similar between the two populations (P = 0.6694) as was status of viral suppression at one year 73% vs. 65%. Conclusion Presence of TDR at baseline had little immediate impact on ART initiation or tolerance, but by limiting choices negatively impacted pill burden and dosing as well as drug costs. Disclosures All authors: No reported disclosures.