title: The incidence rate of HIV type-1 drug resistance in patients on antiretroviral therapy: a nationwide population-based Danish cohort study 1999-2005.
abstract: BACKGROUND
  Newer antiretroviral treatment regimens for HIV carry a lower risk of inducing drug resistance mutations. We estimated changes in incidence rates (IRs) of new mutations in HIV-infected individuals receiving highly active antiretroviral therapy (HAART).
  
  
  METHODS
  Population-based data were obtained from the Danish HIV Cohort Study and the Danish HIV Sequence Database. We included treatment-naive patients initiating HAART after December 1997 and computed time to first drug resistance mutation, identified as new mutations detected within 1 year after a 60-day period of treatment failure (HIV RNA>1,000 copies/ml). We estimated annual IRs of new resistance mutations towards nucleoside reverse transcriptase inhibitors (NRTIs), non-NRTIs (NNRTIs) and protease inhibitors (PI), and of new specific resistance mutations.
  
  
  RESULTS
  A total of 1,829 individuals were observed for 7,294 person-years at risk (PYR). The IR of NRTI resistance decreased from 13.1 per 1,000 PYR (95% confidence interval [CI] 4.9-35.0) in 1999 to 3.7 (1.9-7.2) in 2004-2005 (test for trend P=0.024). The IR of NNRTI resistance decreased from 15.4 (2.2-109.6) in 1999 to 7.9 (4.6-13.6) in 2004-2005 (P=0.077). The IR of PI resistance decreased from 7.5 (1.4-21.8) in 1999 to 2.9 (0.7-11.4) in 2002-2003 (P=0.148). The IRs were low for specific resistance mutations, except for M184V (IR 5.6 [4.0-7.9]) and K103N (IR 8.2 [5.6-12.0]).
  
  
  CONCLUSIONS
  The incidence of acquired drug resistance has decreased among HIV-infected patients treated with HAART in Denmark during 1999-2005.
authors.affiliation: Department of Virology, Statens Serum Institut, Copenhagen, Denmark. aud@ssi.dk
authors.forename: Anne Margrethe
authors.initials: AM
authors.lastname: Audelin
authors.forename: Nicolai
authors.initials: N
authors.lastname: Lohse
authors.forename: Niels
authors.initials: N
authors.lastname: Obel
authors.forename: Jan
authors.initials: J
authors.lastname: Gerstoft
authors.forename: Louise Bruun
authors.initials: LB
authors.lastname: Jørgensen
mesh_terms: D023241:Antiretroviral Therapy, Highly Active; D015331:Cohort Studies; D003718:Denmark / Q000453:epidemiology; D024921:Drug Resistance, Multiple, Viral / Q000235:genetics*; D005260:Female; D015658:HIV Infections / Q000188:drug therapy* / Q000453:epidemiology* / Q000821:virology; D015497:HIV-1 / Q000187:drug effects* / Q000235:genetics; D006801:Humans; D015994:Incidence; D008297:Male; D009154:Mutation; D012367:RNA, Viral / Q000032:analysis / Q000235:genetics; D017211:Treatment Failure
chemical_list: D012367:RNA, Viral