title: Cost-Effectiveness of Combined Sexual and Injection Risk Reduction Interventions among Female Sex Workers Who Inject Drugs in Two Very Distinct Mexican Border Cities.
abstract: BACKGROUND
  We evaluated the cost-effectiveness of combined single session brief behavioral intervention, either didactic or interactive (Mujer Mas Segura, MMS) to promote safer-sex and safer-injection practices among female sex workers who inject drugs (FSW-IDUs) in Tijuana (TJ) and Ciudad-Juarez (CJ) Mexico. Data for this analysis was obtained from a factorial RCT in 2008-2010 coinciding with expansion of needle exchange programs (NEP) in TJ, but not in CJ.
  
  
  METHODS
  A Markov model was developed to estimate the incremental cost per quality adjusted life year gained (QALY) over a lifetime time frame among a hypothetical cohort of 1,000 FSW-IDUs comparing a less intensive didactic vs. a more intensive interactive format of the MMS, separately for safer sex and safer injection combined behavioral interventions. The costs for antiretroviral therapy was not included in the model. We applied a societal perspective, a discount rate of 3% per year and currency adjusted to US$2014. A multivariate sensitivity analysis was performed. The combined and individual components of the MMS interactive behavioral intervention were compared with the didactic formats by calculating the incremental cost-effectiveness ratios (ICER), defined as incremental unit of cost per additional health benefit (e.g., HIV/STI cases averted, QALYs) compared to the next least costly strategy. Following guidelines from the World Health Organization, a combined strategy was considered highly cost-effective if the incremental cost per QALY gained fell below the gross domestic product per capita (GDP) in Mexico (equivalent to US$10,300).
  
  
  RESULTS
  For CJ, the mixed intervention approach of interactive safer sex/didactic safer injection had an incremental cost-effectiveness ratio (ICER) of US$4,360 ($310-$7,200) per QALY gained compared with a dually didactic strategy. Using the dually interactive strategy had an ICER of US$5,874 ($310-$7,200) compared with the mixed approach. For TJ, the combination of interactive safer sex/didactic safer injection had an ICER of US$5,921 ($104-$9,500) per QALY compared with dually didactic. Strategies using the interactive safe injection intervention were dominated due to lack of efficacy advantage. The multivariate sensitivity analysis showed a 95% certainty that in both CJ and TJ the ICER for the mixed approach (interactive safer sex didactic safer injection intervention) was less than the GDP per capita for Mexico. The dual interactive approach met this threshold consistently in CJ, but not in TJ.
  
  
  CONCLUSIONS
  In the absence of an expanded NEP in CJ, the combined-interactive formats of the MMS behavioral intervention is highly cost-effective. In contrast, in TJ where NEP expansion suggests that improved access to sterile syringes significantly reduced injection-related risks, the interactive safer-sex combined didactic safer-injection was highly cost-effective compared with the combined didactic versions of the safer-sex and safer-injection formats of the MMS, with no added benefit from the interactive safer-injection component.
authors.affiliation: University of California San Diego, Department of Medicine, Division of Global Public Health, La Jolla, California, United States of America.|Universidad Autonoma de Baja California, Facultad de Medicina y Psicología, Tijuana, Baja California, México.
authors.forename: Jose L
authors.initials: JL
authors.lastname: Burgos
authors.affiliation: University of California San Diego, Department of Psychiatry, La Jolla, California, United States of America.
authors.forename: Thomas L
authors.initials: TL
authors.lastname: Patterson
authors.affiliation: University of California San Diego, School of Global Policy and Strategy, La Jolla, California, United States of America.
authors.forename: Joshua S
authors.initials: JS
authors.lastname: Graff-Zivin
authors.affiliation: University of California San Francisco, Department of Epidemiology and Biostatistics, Philip R. Lee Institute for Health Policy Studies, Global Health Sciences, San Francisco, California, United States of America.
authors.forename: James G
authors.initials: JG
authors.lastname: Kahn
authors.affiliation: Secretaria de Salud de México, Comision de Salud Fronteriza Mexico-Estados Unidos Sección México, Tijuana, Baja California, México.
authors.forename: M Gudelia
authors.initials: MG
authors.lastname: Rangel
authors.affiliation: Instituto de Servicios de Salud Pública del Estado de Baja California, Mexicali, Baja California, Mexico.
authors.forename: M Remedios
authors.initials: MR
authors.lastname: Lozada
authors.affiliation: Universidad Autonoma de Ciudad Juarez, Facultad de Medicina, Ciudad Juárez, Chihuahua, México.
authors.forename: Hugo
authors.initials: H
authors.lastname: Staines
authors.affiliation: University of California San Diego, Department of Medicine, Division of Global Public Health, La Jolla, California, United States of America.
authors.forename: Steffanie A
authors.initials: SA
authors.lastname: Strathdee
mesh_terms: D018791:CD4 Lymphocyte Count; D002947:Cities; D003362:Cost-Benefit Analysis; D003617:Dangerous Behavior; D055030:Drug Users; D005260:Female; D015658:HIV Infections / Q000453:epidemiology / Q000276:immunology / Q000401:mortality / Q000635:transmission; D006801:Humans; D008800:Mexico; D015233:Models, Statistical; D062486:Public Health Surveillance; D011788:Quality of Life; D040242:Risk Reduction Behavior; D060386:Sex Workers; D012725:Sexual Behavior