title: Predictors of having a resistance test following confirmed virological failure of combination antiretroviral therapy: data from EuroSIDA.
abstract: BACKGROUND
  Guidelines suggest that patients on continuous antiretroviral therapy for >4 months with current viral load (VL)>1,000 copies/ml should be tested for resistance. There are limited data showing the frequency of resistance testing in routine clinical practice following these recommendations.
  
  
  METHODS
  In EuroSIDA, virological failure (VF) was defined as confirmed VL>1,000 copies/ml after ≥ 4 months continuous use of any antiretroviral in a ≥ 3-drug regimen started during or after 2002. We assessed whether a resistance test was performed around VF (from 4 months before to 1 year after VF) and used logistic regression analysis to assess factors associated with having a resistance test.
  
  
  RESULTS
  A total of 1,090 patients experienced VF a median 8.1 months (range 4 months to 6.3 years) after starting their regimen. There were 395 (36.2%; 95% CI 33.4-39.1) patients with a resistance test around the time of VF. Predictors of having a resistance test following VF include availability of a resistance test earlier than 4 months before VF (OR 2.20, 95% CI 1.77-2.75 for yes versus no; P<0.0001), region (OR 0.29, 95% CI 0.14-0.62 for Eastern Europe versus Northern Europe and OR 0.64, 95% CI 0.48-0.85 for Southern Europe versus Northern Europe; global P=0.0006) and current calendar year (OR 0.45, 95% CI 0.30-0.68 for ≥ 2007 versus 2004; global P=0.003).
  
  
  CONCLUSIONS
  This analysis suggests a delay in genotypic testing after VF that seems longer than expected given current treatment guidelines. This delay is highly variable across Europe.
authors.affiliation: Copenhagen HIV Programme, Copenhagen, Denmark. z.fox@ucl.ac.uk
authors.forename: Zoe V
authors.initials: ZV
authors.lastname: Fox
authors.forename: Alessandro
authors.initials: A
authors.lastname: Cozzi-Lepri
authors.forename: Antonella
authors.initials: A
authors.lastname: D'Arminio Monforte
authors.forename: Anders
authors.initials: A
authors.lastname: Karlsson
authors.forename: Andrew N
authors.initials: AN
authors.lastname: Phillips
authors.forename: Gitte
authors.initials: G
authors.lastname: Kronborg
authors.forename: Jesper
authors.initials: J
authors.lastname: Kjaer
authors.forename: Bonaventura
authors.initials: B
authors.lastname: Clotet
authors.forename: Jens D
authors.initials: JD
authors.lastname: Lundgren
mesh_terms: D000328:Adult; D019380:Anti-HIV Agents / Q000627:therapeutic use*; D024882:Drug Resistance, Viral; D004359:Drug Therapy, Combination; D005260:Female; D015658:HIV Infections / Q000188:drug therapy* / Q000453:epidemiology / Q000821:virology; D017320:HIV Protease Inhibitors / Q000627:therapeutic use; D015497:HIV-1 / Q000187:drug effects; D006801:Humans; D008297:Male; D008875:Middle Aged; D012307:Risk Factors; D013997:Time Factors; D017211:Treatment Failure; D019562:Viral Load
chemical_list: D019380:Anti-HIV Agents; D017320:HIV Protease Inhibitors