Cost-Effectiveness of Combined Sexual and Injection Risk Reduction Interventions Among Female Sex Workers Who Inject Drugs in Two Very Distinct Mexican Border Cities

Burgos, J, T Patterson, J Graff Zivin, J Kahn, G Rangel, R Lozada, H Staines, and S Strathdee, “Cost-Effectiveness of Combined Sexual and Injection Risk Reduction Interventions Among Female Sex Workers Who Inject Drugs in Two Very Distinct Mexican Border Cities” PloS One, 11(2016), e0147719.

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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 FSWIDUs 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).
Findings
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.
Interpretation
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.