title: Regional differences in rates of HIV-1 viral load monitoring in Canada: Insights and implications for antiretroviral care in high income countries.
abstract: BACKGROUND
  Viral load (VL) monitoring is an essential component of the care of HIV positive individuals. Rates of VL monitoring have been shown to vary by HIV risk factor and clinical characteristics. The objective of this study was to determine whether there are differences among regions in Canada in the rates of VL testing of HIV-positive individuals on combination antiretroviral therapy (cART), where the testing is available without financial barriers under the coverage of provincial health insurance programs.
  
  
  METHODS
  The Canadian Observational Cohort (CANOC) is a collaboration of nine Canadian cohorts of HIV-positive individuals who initiated cART after January 1, 2000. The study included participants with at least one year of follow-up. Generalized Estimating Equation (GEE) regression models were used to determine the effect of geographic region on (1) the occurrence of an interval of 9 months or more between two consecutive recorded VL tests and (2) the number of days between VL tests, after adjusting for demographic and clinical covariates. Overall and regional annual rates of VL testing were also reported.
  
  
  RESULTS
  3,648 individuals were included in the analysis with a median follow-up of 42.9 months and a median of 15 VL tests. In multivariable GEE logistic regression models, gaps in VL testing >9 months were more likely in Quebec (Odds Ratio (OR) = 1.72, p < 0.0001) and Ontario (OR = 1.78, p < 0.0001) than in British Columbia and among injection drug users (OR = 1.68, p < 0.0001) and were less likely among older individuals (OR = 0.77 per 10 years, p < 0.0001), among men having sex with men (OR = 0.62, p < 0.0001), within the first year of cART (OR = 0.15, p < 0.0001), among individuals on cART at the time of the blood draw (OR = 0.34, p < 0.0001) and among individuals with VL < 50 copies/ml at the previous visit (OR = 0.56, p < .0001).
  
  
  CONCLUSIONS
  Significant variation in rates of VL testing and the probability of a significant gap in testing were related to geographic region, HIV risk factor, age, year of cART initiation, type of cART regimen, being in the first year of cART, AIDS-defining illness and whether or not the previous VL was below the limit of detection.
authors.affiliation: Dalla Lana School of Public Health, University of Toronto, Toronto, Canada. raboud@lunenfeld.ca
authors.forename: Janet M
authors.initials: JM
authors.lastname: Raboud
authors.forename: Mona R
authors.initials: MR
authors.lastname: Loutfy
authors.forename: DeSheng
authors.initials: D
authors.lastname: Su
authors.forename: Ahmed M
authors.initials: AM
authors.lastname: Bayoumi
authors.forename: Marina B
authors.initials: MB
authors.lastname: Klein
authors.forename: Curtis
authors.initials: C
authors.lastname: Cooper
authors.forename: Nima
authors.initials: N
authors.lastname: Machouf
authors.forename: Sean
authors.initials: S
authors.lastname: Rourke
authors.forename: Sharon
authors.initials: S
authors.lastname: Walmsley
authors.forename: Anita
authors.initials: A
authors.lastname: Rachlis
authors.forename: P Richard
authors.initials: PR
authors.lastname: Harrigan
authors.forename: Marek
authors.initials: M
authors.lastname: Smieja
authors.forename: Christos
authors.initials: C
authors.lastname: Tsoukas
authors.forename: Julio S G
authors.initials: JS
authors.lastname: Montaner
authors.forename: Robert S
authors.initials: RS
authors.lastname: Hogg
mesh_terms: D000328:Adult; D000367:Age Factors; D019380:Anti-HIV Agents / Q000627:therapeutic use*; D002170:Canada; D016903:Drug Monitoring / Q000706:statistics & numerical data*; D005260:Female; D005843:Geography; D015658:HIV Infections / Q000175:diagnosis / Q000188:drug therapy* / Q000821:virology*; D015497:HIV-1 / Q000302:isolation & purification*; D018451:Homosexuality, Male; D006801:Humans; D008297:Male; D008875:Middle Aged; D015819:Substance Abuse, Intravenous; D019562:Viral Load
chemical_list: D019380:Anti-HIV Agents