Cost-effectiveness of an intervention to reduce HIV/STI incidence and promote condom use among female sex workers in the Mexico-US border region

Abstract

Background: Previous research demonstrated efficacy of a brief behavioral intervention to reduce incidence of HIV and sexually transmitted infections (STIs) among female sex workers (FSWs) in Tijuana and Ciudad Juarez, Mexico, cities on Mexico's border with the US. We assessed this intervention's cost-effectiveness.

Methodology and principal findings: A life-time Markov model was developed to estimate HIV cases prevented, changes in quality-adjusted life expectancy (QALE), and costs per additional quality-adjusted life year gained (QALY), comparing (in US$2,009) no intervention to a once-only and annual intervention. Future costs and health benefits were discounted annually at 3%. Sensitivity analyses evaluated model robustness. We found that for a hypothetical 1,000 FSWs receiving the once-only intervention, there were 33 HIV cases prevented and 5.7 months of QALE gained compared to no intervention. The additional cost per QALY gained was US$183. For FSWs receiving the intervention annually, there were 29 additional HIV cases prevented and 4.5 additional months of QALE compared to the once-only intervention. The additional cost per QALY was US$1,075. When highly active antiretroviral therapy (HAART) was included in the model, the annual intervention strategy resulted in net savings and dominated both once-only and no intervention strategies, and remained robust across extensive sensitivity analyses. Even when considering clinical benefits from HAART, ignoring added costs, the cost per QALY gained remained below three times the Mexican GDP per capita, and below established cost-effectiveness thresholds.

Conclusions/significance: This brief intervention was shown to be cost-effective among FSWs in two Mexico-US border cities and may have application for FSWs in other resource-limited settings.

Trial registration: ClinicalTrials.gov NCT00338845.

Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Figure 1. CONSORT flow chart.

* All participants who completed follow-up were analyzed for STI incidence. Some participants were lacking follow-up sexual risk data. See Table 2, p. 2054, in Patterson et al. (2008), Am J Public Health 98: 2051–2057 for details.

Figure 2. Schematic representation of the Markov model used for the cost effectiveness analysis for the Mujer Segura intervention.

a = Female sex workers; b = No HIV or sexually transmitted infections; c = Gonorrhea or Chlamydia trachomatis infection; d = Syphilis infection; e = HIV infection (no other sexually transmitted infections); f = HIV and gonorrhea or Chlamydia co-infection; g = HIV and syphilis co-infection.

Figure 3. Tornado Diagram showing results of one way sensitivity analyses comparing no intervention to the Mujer Segura intervention offered once only.

The vertical dotted line represents the base-case analysis incremental cost per QALY (quality-adjusted life years) gained. The numbers at the end of each bar represents the range over which each of the variables was changed. a = Changes in annual discount rate used for costs and health benefits; b = Incidence is presented per 100 person-years; c = quality adjusted life years.

Figure 4. Tornado Diagram showing results of one way sensitivity analyses comparing the Mujer Segura intervention offered once only and annually.

The vertical dotted line represents the base-case analysis incremental cost per QALY (quality-adjusted life years) gained. The numbers at the end of each bar represents the range over which each of the variables was changed. a = Changes in annual discount rate used for costs and health benefits; b = Incidence is presented per 100 person-years; c = quality adjusted life years.

Figure 5. Cost-effectiveness acceptability curve for the Mujer Segura intervention offered once or annually.

Results of the probabilistic sensitivity analysis, represented as a cost-effectiveness acceptability curve. The cost per QALY (quality adjusted life years) gained from the Mujer Segura intervention is plotted on the x-axis, and the probability that the intervention is cost-effective across these values is plotted on the y-axis. The Mujer Segura intervention offered once or annually resulted in a cost-effectiveness below a willingness to pay treshold of three times the GDP in Mexico per QALY gained (equivalent to US$29,300). a = Mujer Segura behavioral intervention; b = Quality adjusted life year.