title: Time to Viremia for Patients Taking their First Antiretroviral Regimen and the Subsequent Resistance Profiles.
abstract: BACKGROUND
  The resistance profiles for patients on first-line antiretroviral therapy (ART) regimens after viremia have not been well studied in community clinic settings in the modern treatment era.
  
  
  OBJECTIVE
  To determine time to viremia and the ART resistance profiles of viremic patients.
  
  
  METHODS
  HIV-positive patients aged ≥16 years initiating a three-drug regimen were retrospectively identified from 01/01/06 to 12/31/12. The regimens were a backbone of two nucleoside reverse transcriptase inhibitors (NRTIs) and a third agent: a protease inhibitor (PI), non-nucleoside reverse transcriptase inhibitor (NNRTI), or an integrase inhibitor (II). Time to viremia was compared using a proportional hazards model, adjusting for demographic and clinical factors. Resistance profiles were described in those with baseline and follow-up genotypes.
  
  
  RESULTS
  For 653 patients, distribution of third-agent use and viremia was: 244 (37%) on PIs with 80 viremia, 364 (56%) on NNRTIs with 84 viremia, and 45 (7%) on II with 11 viremia. Only for NNRTIs, time to viremia was longer than PIs (p = 0.04) for patients with a CD4 count ≥200 cells/mm(3). Of the 175 with viremia, 143 (82%) had baseline and 37 (21%) had follow-up genotype. Upon viremia, emerging ART resistance was rare. One new NNRTI (Y181C) mutation was identified and three patients taking PI-based regimens developed NRTI mutations (M184 V, M184I, and T215Y).
  
  
  CONCLUSIONS
  Time to viremia for NNRTIs was longer than PIs. With viremia, ART resistance rarely developed without PI or II mutations, but with a few NRTI mutations in those taking PI-based regimens, and NNRTI mutations in those taking NNRTI-based regimens.
authors.affiliation: 1 Maple Leaf Medical Clinic , Toronto, Canada.
authors.forename: Frederic
authors.initials: F
authors.lastname: Crouzat
authors.forename: Anita C
authors.initials: AC
authors.lastname: Benoit
authors.forename: Colin
authors.initials: C
authors.lastname: Kovacs
authors.forename: Graham
authors.initials: G
authors.lastname: Smith
authors.forename: Nathan
authors.initials: N
authors.lastname: Taback
authors.forename: Ina
authors.initials: I
authors.lastname: Sandler
authors.forename: Megan
authors.initials: M
authors.lastname: Acsai
authors.forename: William
authors.initials: W
authors.lastname: Barrie
authors.forename: Jason
authors.initials: J
authors.lastname: Brunetta
authors.forename: Benny
authors.initials: B
authors.lastname: Chang
authors.forename: David
authors.initials: D
authors.lastname: Fletcher
authors.forename: David
authors.initials: D
authors.lastname: Knox
authors.forename: Barry
authors.initials: B
authors.lastname: Merkley
authors.forename: Malika
authors.initials: M
authors.lastname: Sharma
authors.forename: David
authors.initials: D
authors.lastname: Tilley
authors.forename: Mona
authors.initials: M
authors.lastname: Loutfy
mesh_terms: D000328:Adult; D019380:Anti-HIV Agents / Q000008:administration & dosage / Q000627:therapeutic use*; D024882:Drug Resistance, Viral; D005260:Female; D015658:HIV Infections / Q000097:blood / Q000188:drug therapy*; D015497:HIV-1 / Q000187:drug effects*; D006801:Humans; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D019562:Viral Load; D014766:Viremia
chemical_list: D019380:Anti-HIV Agents
keywords: HIV; first-line antiretroviral therapy; resistance mutations; viremia