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As antiretroviral treatment (ART) for HIV/AIDS is scaled-up globally, information on per-person costs is critical to improve efficiency in service delivery and maximize coverage and health impact.
To review studies on delivery unit costs for adult and pediatric ART provision per-patient-year, and prevention of mother-to-child transmission (PMTCT) interventions per mother-infant pair screened or treated, in low- and middle-income countries.
Systematic review of English, French and Spanish publications from 2001 to 2009, reporting empirical costing that accounted for at least antiretroviral (ARV) medicines, laboratory testing and personnel. Expenditures were analyzed by country income level and cost component. All costs were standardized to 2009 US dollars.
Analyses covered 29 eligible, comprehensive costing studies. In the base case, in low-income countries (LIC), median, ART cost per patient-year was $792 (mean: $839, range: $682-$1089); for lower-middle-income countries (LMIC), the median was $932 (mean: $1246, range: $156-$3904); and for upper-middle-income countries (UMIC) the median was $1454 (mean: $2783, range: $1230-$5667). ARV drugs were largest component of overall ART cost in all settings (62%, 50% and 47% in LIC, LMIC and UMIC respectively). Out of 26 ART studies, 14 report which drug regimes were used, and only one study explicitly reported second line treatment costs. The second cost driver was laboratory cost in LIC and LMIC (14% and 19.5%) whereas it was personnel costs in UMIC (26%). Two studies specified the types of laboratory tests costed, and three studies specifically included above-facility-level personnel costs. Three studies reported detailed PMTCT costs, and two studies reported on pediatric ART.
There is a paucity of data on the full ART and PMTCT delivery unit costs, in particular for low-and middle-income countries. Heterogeneity in activities costed and insufficient detail regarding components included in the costing hampers standardization of unit cost measures. Evaluation of program-level unit costs would benefit from international guidance on standardized costing methods, and expenditure categories and definitions. Future work should help elucidate the sources for the large variations in delivery unit costs across settings with similar income and epidemiological characteristics.
Cost evaluations support program planning and budgeting, can help to ensure program sustainability, and are a pre-requisite in identifying opportunities for efficiency gains. [1, 2] As global health institutions strive to ensure “value for money,” they are committed to supporting countries to measure per-person delivery costs of key services.[3–8] Since 2008, many national HIV/AIDS programs have made an important advance in complying with the bi-annual routine reporting of nationally aggregated expenditures as stated in the 2001 Declaration of Commitment on HIV/AIDS (UNGASS) to UNAIDS. However, UNGASS reporting does not express program expenditures as per-person unit costs, nor does it request a comprehensive break-down of the cost components included in each service area. As of 2010, most HIV/AIDS programs do not routinely assess their cost per person or per unit of service delivery, nor do they have expenditure breakdowns by cost components using standardized methods.
For antiretroviral treatment (ART), scale-up of treatment access in low- and middle-income studies started in 2004–5, when funding increased substantially with new donor funding from the Global Fund to Fight AIDS, Tuberculosis and Malaria, and the U.S. President’s Emergency Plan for AIDS Relief (PEPFAR), among others. As of the end of 2009, an estimated 5.2 million HIV-infected people were receiving ART globally; with the WHO’s revised 2010 guidelines on HIV treatment in resource-limited settings, the total immediate need is now estimated at 15 million eligible people worldwide. The ongoing scale-up and progress toward Universal Access will depend on both total available funding and the delivery cost per patient-year in high-HIV countries.
Previous reviews of ART – facility-level or per-patient – costs found only a very small number of studies from low- and middle-income countries [11, 12] and estimated the cost of antiretroviral (ARV) medicines from manufacturers’ procurement price lists, as an average per country income-group. For Prevention of Mother-to-Child Transmission of HIV (PMTCT), (unit) delivery costs have not been reviewed since 2000. The most recent ART costs review  included more studies from low- and middle-income countries and presented a scoring system to rate studies’ methodological quality – without attempting a quantitative meta-analysis of cost results.
To complement these overviews, we conducted a systematic literature review and a meta-analysis of per-patient unit expenditures on adult and pediatric ART as well as ARV prophylaxis used for PMTCT, using explicit guidelines for systematic reviews, and standardizing data from eligible studies into common service delivery units and cost component categories. Per-patient costs are presented as median, arithmetic average, and ranges across eligible study sites, studies, countries and country-income-level groupings, separately for the most important standardized cost components. We discuss results in the light of information requirements anticipated from National AIDS Programs from major global financiers of HIV/AIDS program scale-up.
The literature search followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Original articles published in English, French and Spanish from January 2001 to October 2009 were searched using PubMed, EconLit and Cochrane Library, and gray literature through Google Scholar and POPLINE. In addition, websites of international donor organizations such as UNAIDS, WHO, World Bank, PEPFAR, UNICEF were searched. We also screened abstracts from the International AIDS Conferences 2001–2008, International Health Economics Association 2006–2008, American Society for Health Economists 2006–08, International AIDS Economics Network 2008, and PEPFAR Implementer’s meetings 2008–09 for contextual information to the published data. References identified as relevant served to track additional studies of interest. Annex A (all annexes available in Supplemental Digital Contents only) details the search terms used on electronic databases. Annex B shows the search commands and number of studies found.
Eligible articles were reviewed for inclusion by at least two independent reviewers (OG and VW or AML), using a pre-determined data extraction form (see Annex C). When the decision was “in doubt”, a third or fourth reviewer (YST or AFL) analyzed the article; inclusion was solved by consensus. If the information contained in the full-text article was incomplete, its authors were contacted to obtain missing data.
ART delivery unit cost data were standardized as estimates per patient-year, separately for first-line and second-line ART, or weighed by their local mix of patients. Pediatric ART was distinguished from adult ART using an age cut-off of 15 years. Components of total costs were categorized as follows:
For PMTCT, reported costs were either per HIV-infected pregnant woman receiving ARV prophylaxis, or per pregnant woman initially tested and counseled for HIV. In each case, costs covered the woman-neonate pair throughout the pregnancy/birth period. Cost components were categorized as follows:
We report all costs in October 2009 US dollars (USD), after foreign currency conversion using average annual exchange rates provided by original study authors or from the International Monetary Fund (except, in the case of a study of ART in Lesotho, directly from a Central Bank source for lack of the relevant exchange rate from the IMF). Once converted into USD, costs were adjusted for inflation using the U.S. Consumer Price Index (CPI).
The analysis focused on economic costs from the perspective of the provider. Specified economic costs to the patient were included only if a monetary transaction took place so that the service would occur (e.g., a co-payment or recuperation fee paid for by the patient); in which case they were added to the overall costs.
Unit costs and unit cost components were summarized as mean, median and range across countries studied (after aggregation across multiple sites, or data points within each country), within country income level groups: low-income countries (LIC), lower-middle-income countries (LMIC), and upper-middle-income countries (UMIC), according to the World Bank’s 2009 country classification. This method of aggregation prevented countries with relatively large numbers of data points to skew the results. In sensitivity analyses, we explored the robustness of results against alternative ways of aggregating results across sites, countries and country-income groupings, and of different study inclusion criteria.
Out of 574 abstracts retrieved, 150 full-text studies were assessed for eligibility; of those, 29 were included in analysis: 26 on ART (23 on adult ART, two on adult and pediatric ART[21, 22], and one on pediatric ART only)  (tables I, ,IIII and III). Table IV provides results for the base case and the sensitivity analysis for ART unit costs, and fig. 2 summarizes the most relevant findings. Three studies for PMTCT are detailed in table V. (Expanded versions of tables with additional information and annexes are available as Supplemental Digital Content).
Six studies from four low-income countries (LIC) were included (Benin, Ethiopia, Haiti and Uganda); the median cost per patient-year of ART was $792 (mean $839, range $682 to $1,089) (tables I & IV).[22, 24–28] Studies for lower-middle-income countries (LMIC) were found for India[29, 30], Lesotho, Morocco, Nigeria[32, 33], and Thailand ; the median cost of ART was $932 (mean $1,246, range $156 to $3,904) (tables II & IV). In upper-middle-income countries (UMIC), Brazil [23, 35], Mexico [36–38] and South Africa [21, 39–45] the median ART cost was $1,454 (mean $2,783; range $1,230 to $5,667) (tables III & IV).
ART unit costs and its components varied considerably both between countries and studies,– such as South Africa[21, 39–45] – and between sites within one study (e.g., Gupta et al, 2009) (fig. 2). While variations between studies may in part reflect differences in costing methods and definitions, variations within studies point to the existence of real differences in actual cost between sites and/or patient populations.
In all three income groups, ARV medicines were the largest cost component. In low-income countries, they represented 64% of the overall costs, at a median $428 per patient-year (mean: $456 (62%), range: $205–$607 (37% – 78%)) (table I). In lower-middle income countries, ARV medicines represented 50% of overall cost at a median $127 (mean: $463 (54%), range: $46–$3415 (35%–88%)) (table II). In upper-middle income countries, ARV medicines covered 47% of cost, at a median $958 per patient-year (mean: $1473 (53%), range: $104 – $6,024 (4%–96%)) (table III).
In LIC and LMIC, laboratory costs were the second most important cost component. In LIC they accounted for 14% of overall costs (median $123; mean: $133 (17%), range: $16 – $242 (6–30%)) (table I). In LMIC laboratory costs corresponded to 20% of overall costs (median cost of $42; mean: $106 (18%), range: <$1 – $462 (<1% – 32%)) (table II). In UMIC, laboratory costs accounted for 10% (median of $223; mean: $319 (14%), range: $40 – $1174 (3% – 41%) of ART cost (table III), being the third largest cost component after personnel.
In LIC and LMIC, personnel costs were the third most important cost component, corresponding to 3% in LIC [median $22; mean: $66 (9%), range: $12 – $243 (1%–29%)], (table I), and 8% in LMIC [median $12; mean: $82 (13%), range: $7–$391 (6%–38%)], (table II) of overall costs, respectively. In UMIC, in contrast, personnel costs were the second most important cost component at 26% of overall cost [median cost of $383; mean: $535 (24%), range: $6 – $2098 (0.4% – 55%)] (table III).
Most studies for ART (23 out of 26) included the cost of personnel only at the facility level. While types of services costed varied, only seven studies reported details of the types of personnel included [26, 30, 35, 39, 41, 43, 44]. Of these, three costing studies included above-facility level personnel such as human resources at distribution centers or district/provincial/national program management, or monitoring and evaluation in the personnel cost component.[29, 30, 33] (See section 3.1D below).
Three studies included program-level costs associated with ART delivery.[29, 30, 33] Across two urban sites in India  program-level costs on medical and administrative personnel other than those directly involved in ART delivery to patients were reported to be about 16% of per patient-year recurrent costs during the first year of the program, falling to about 7% in the second year. Another study in India included a project coordinator working across different health facilities under personnel cost. In urban Nigeria, reported above-facility expenses included transport of drugs from federal central facilities to the ARV centers.
We identified two studies reporting costs of ART for patients below 15 years of age. In UMIC Brazil, costs of ART in a university hospital were $2,039 per year for outpatient children ; weighed across all children (14% of whom were inpatient), the average yearly cost was $2,826. In LIC Ethiopia  a total cost per child-year was found of $961 for new patients (within first 6 month of treatment) and $933 for established patients, with ARVs covering $607 (over 60% of total cost), and laboratory tests $191 (20%) in new or $94 (10%) in established patients.
Three eligible PMTCT costing studies were analyzed. The cost per mother-neonate pair receiving nevirapine around child delivery was $251 in India, $ 209 in South Africa  (both middle-income countries), but only $6.4 in Rwanda, a LIC (table V). (The large difference in cost in the latter study suggests that not all components were comparable).
The South Africa study presented a thorough costing in already existing facilities, focusing on the added financial costs utilized specifically by the PMTCT program. Across four facilities, the average unit cost per HIV-infected mother-neonate pair receiving prophylactic nevirapine services was $209. This cost included nevirapine to mothers at delivery, as well as provision of nevirapine suspension to the infant and formula milk for the duration of the hospital stay. Additional costs estimated in the study were: $42.4 for the pre-test counseling, and $32.5 for testing costs. The study reported a substantially higher cost for post-discharge follow-up care at $327 per HIV-infected mother/infant pair covering cotrimoxazole and provision of infant formula after birth for the duration of the hospital stay (table V). The unit costs varied according to the denominator unit used (pregnant women screened, women tested, HIV-infected women and neonate pair, number followed) as well as between the four locations according to their economic and epidemiological differences: e.g., a high HIV prevalence, resource-poor setting (Frankfort, Free State) compared to a low-HIV-prevalence, better resourced setting (Paarl, Western Cape).
In Andhra Pradesh, India across 16 PMTCT centers 1,212 HIV-infected pregnant women received PMTCT, out of 125,073 pregnant women counseled and tested. The average economic cost per HIV-infected woman receiving nevirapine around child delivery was $251. Expressed per pregnant women counseled and tested irrespective of HIV status, average unit cost was $2.40. Given the low price of nevirapine, personnel was the major cost component, at $119 or 47% of overall cost per HIV-infected woman, followed by $37 (15%) on overhead.
In Rwanda, the PMTCT unit cost was much lower, at $6.4 for a specific intervention. This marked contrast is in part explained by Rwanda’s much lower per-capita income level and health worker salaries. Equally important, this unit cost was achieved in a large-scale program in a high-HIV prevalence setting, with the six health centers covering a catchment population of 148,151 persons with a high PMTCT uptake rate of 71.6% that likely achieved significant economies of scale. However, the study does not specify number of pregnant women screened for PMTCT, the number of HIV-infected women, or the number of mother-infant pairs given NVP.
A first sensitivity analysis assessed the effect of aggregating unit cost within country income groups by weighing all data points and sites across studies and countries equally, instead of the base-case model (presented above) that weighed all countries equally irrespective of their number of data points. In this variant model, median unit costs of ART were nearly unchanged for LIC and UMIC: in LIC the median was $797 (compared to $792 in base-case model) and for UMIC 1,397 (compared to $1,454 in base-case model, table IV). For LMIC, however, this alternative aggregation method resulted in a three-fold reduced median cost estimate per patient-year, of $298 compared to $932 in the base-case. This difference reflects an overrepresentation of study sites and data points from India among LMIC, with exceptionally low unit costs reflecting India’s uniquely low ARV prices related to the country’s important generic ARV industry and resulting strong pharmaceutical negotiation capacity.
A second sensitivity analysis, to further check on representativeness, expanded the data set to include a number of studies which did not include a break-down of cost components, but had data on total ART costs. Adding one study from Kenya, the LIC median cost per patient per year became $773 (mean $713, range $211 to $1,089), similar to the original estimate of $ 792. Among LMIC, adding data points from Thailand and India [51–53] did not alter the median cost per patient per year from default of $932 (but the mean increased to $1,314; range $162 to $4212).
Third, we replaced the country income classification according to each country’s 2009 income level by a classification using each country’s income level in the year of cost data collection (while in both cases applying World Bank’s 2009 income thresholds). This shifted five countries that had grown richer between the costing study year and 2009 (Brazil, India, Lesotho, Nigeria, and South Africa) into a lower income category. This country regrouping reduced the median ART per-patient cost among LIC (from $792 to $646), increased the estimate for LMIC (from $932 to $1,454) and decreased the estimate for UMIC (from $1,454 to $1,241).
Empirical data on ART delivery unit costs in low- and middle-income countries has increased significantly in recent years, as access to ART has expanded. The current review identifies several more good-quality costing studies of both outpatient and home-based ART than earlier reviews [11, 12, 14], and provides cost estimates for the components ARVs, personnel and laboratory costs separately.
The results have several implications for program planning and budgeting, and for seeking efficiency improvement. For ART, within health facilities the key cost drivers are ARV procurement, laboratory tests, and staff. ARV prices have declined substantially over the last decade, with average declines of 12–39% over 2006–2009 for the first-line regimens most commonly used in low- and middle-income countries. Lacking specification of regimens and drug sources in sites studied, it was not possible to adjust cost estimates for price declines. Only 6 out of the 24 ART costing studies reported whether the program used generic or innovator drugs (see SDC version of tables I, ,IIII and III). Of 14 studies that specified ARV regimens, the majority used lamivudine (3TC) + nevirapine (NVP) + stavudine (d4T) as the most common first-line regimen, the regimen for which recent price declines have been smallest: 9–12% per year.  The predominance of this regimen may explain why over 2004–2009, the average proportion of overall ART cost covered by ARV drugs was relatively stable, at 48–52% every year, rather than declining.
The observed large variations between countries and sites in laboratory costs point to possible opportunities for efficiency seeking. Part of variations may relate to differing clinical stage of patients and response to treatment , with high laboratory costs during the first 6 months after ART initiation. Further, laboratory costs tend to be lower in established programs or in hospitals, for example, $15.7 or 6% of overall cost in Ethiopia in 2004–5 , compared to starting programs or clinics that are investing more in laboratory equipment.
Available data (tables I—III) were limited in the specification of laboratory tests performed, test-specific costs as well as in the specification of precise laboratory testing practices and frequencies. We could therefore not analyze whether sites with routine, systematic CD4 and viral load monitoring were more expensive than sites with selective viral load monitoring, sites with only (or less frequent) CD4, or sites with just clinical monitoring, so we cannot estimate the likely savings from shifting testing patterns. In the trial of clinically-driven versus laboratory-guided ART (DART) in Uganda and Zimbabwe, hematology and biochemistry added little benefit; 12-weekly CD4 monitoring improved clinical outcomes from the 2nd year from treatment initiation onwards. Based on minimal lab monitoring (i.e., CD4 12-weekly after the second year), the cost of CD4 testing would have to drop to $3.8 (from current $175) in order to make laboratory monitoring cost-effective.  
Another approach to improving ART program efficiency may be personnel task shifting. [57–59] In an NGO-led program in rural Uganda, costs to the provider were similar for clinic-based and home-based ART ($834 and $789 per patient-year, respectively), at comparable patient retention and clinical outcomes . The study suggests an opportunity to scale-up ART access in settings with restrained health system capacity. The markedly higher cost of inpatient compared to outpatient ART (in 2 studies in South Africa, table III) furthermore demonstrates the financial importance of preventing hospitalizations.
This review reflects the state of evidence in the first decade of global ART scale-up. Given the limited number of studies, from selected countries and settings, the available data could hardly claim global representativeness. Despite the recent increase in good-quality studies (as defined in our inclusion criteria), costing information remains extremely limited in South Asia (N=2 studies), Latin America and the Caribbean (N=5) and East Asia and the Pacific (N=1). Also, in sub-Saharan Africa, 8 out of the 16 studies were conducted in South Africa, which by its relatively high income level is the country least representative of the region. The lack of regional representativeness is one reason why our first sensitivity analysis found higher median ART costs in low-income countries compared to lower-middle-income countries, a result that seems contrary to intuition and to observed patterns in ARV prices. Despite the inclusion of studies from the gray literature (of which 7 were found eligible [18, 21, 22, 26, 32, 33, 38]), we cannot exclude the possibility of publication bias in available costing studies. Several recent, well-executed ART and PMTCT cost studies that are recognized for influencing donor funding policies have not been published in books, peer-reviewed journals, or made otherwise publically available, so were unfortunately not included in our meta-analyses.
Innovative Monitoring & Evaluation strategies are needed to address the gaps in good-quality evidence, especially concerning above-facility and program-level costs. We intended to analyze all relevant cost components, including program–level (above-facility-level) activities and expenses including managerial overheads, administration, monitoring and evaluation and training borne at district, province and national levels. Only three ART studies however provided such programmatic costs, without sufficient description of the relevant activities or cost items to analyze the determinants of these potentially significant contributions to overall delivery cost.
Among available costing studies, quality and completeness varied. Many studies did not explicitly report all cost components, missing information on important cost determinants such as ARV drugs, regimens, type and frequency of laboratory testing used. Most studies also lacked details about variation in costs between different types of facilities and patient populations studied (in terms of e.g., age and CD4 cell count at treatment initiation). Basic information on cost components was lacking in many studies; often either capital costs (such as those related to setting up laboratory equipment), or selected recurrent costs (like utilities) were omitted. In particular, definitions of overhead costs varied, with some studies not even including any overheads. Only three studies [32, 33, 35] mentioned explicitly that their data collection instruments had been validated or piloted before application. The best studies reviewed use a micro-costing approach, where expenditures on each component of providing ART or PMTCT delivery are separately listed and costed out. Even when an ingredients approach was utilized, most studies in the last decade do not provide the type of ART used (not even generic vs. patent, or first-line as distinct from second-line). In many studies sample sizes appear to have been driven by clinical outcomes, rather than by costing-related statistical considerations. Sample sizes varied between 209 (median for LIC, range 122–218) and 430 patients (median for UMIC, range 22 to 2,835), which may be considered appropriate for an overall estimate from one single locality. However, convenience sampling limits the precision and power to evaluate costs for relevant strata of sites, patient age groups, treatment regimens and modality and phases of treatment.
Heterogeneity in unit denominators, notably the calculation of patient-years, further complicates comparisons among studies. For illustration, a study in India  reported 1,094 clients who “ever started ART” (as average across sites), 939 clients “at the end of study” and 503 clients who had been “on therapy for the entire study period”. These authors selected the corresponding 9,460 client-months of ART as appropriate denominator unit; however the large differences between patients starting and retained illustrates the critical influence that varying denominator calculations will have on unit cost estimates, especially in programs with low patient retention and/or rapid scale-up with many new patients initiating ART.
The limitations in availability and comparability of existing cost data described above highlight an urgent need for development and dissemination of standardized cost measurement methodologies and for capacity building. Awaiting such guidance and improved data quality and standardization, any cost comparisons between sites and studies should only be done with extreme caution and attention to methodological differences; interpretations on relative efficiency will typically be limited to within-study determinants. Future strategic use of cost data for improving the efficiency of ART delivery will in particular benefit from more careful costing and reporting of ARV drugs sources and regimens, laboratory costs by type and frequency of tests, and of staff costs by type of personnel including those above the health facility level).
Future assessments should link costs to health outcomes, including cost differentials associated with clinical response, drug toxicity and resistance . This is ever more important in view of the WHO’s revised 2010 guidelines for adult ART in resource-limited settings, which recommend an expanded access to ART starting at CD4 cell count below 350/uL instead of the former 200/uL. In addition, a gradual phasing-out is now recommended of stavudine (d4T) in first-line regimens, to be replaced by less toxic but more costly efavirenz and/or tenofovir-based first-line regimens . As countries will over coming years gradually adopt and implement the new treatment guidelines, it is imperative that costing studies document the mix of patients evaluated in terms of CD4 cell counts at treatment initiation and regimens used, to facilitate interpretation of cost findings and cost determinants.
To improve the knowledge base on efficient ART and PMTCT delivery, collaboration between countries could be very important: First, to increase costing capacity and resources, and second, to exchange experiences in increasing service efficiency. Multi-country exercises should help to improve and standardize costing methodologies and tools for comprehensive data collection. Economies of scale as apparent in some settings  are worth investigating, to establish more clearly if these are achieved merely by allocating fixed costs over a larger number of patients, or by improved technical efficiency (i.e. transformation of inputs to outputs) associated with program maturation and learning.
Whenever possible (conditional on the availability of data on patient wages and other opportunity costs), both financial and economic costs should be collected. Financial costs are relevant for programmatic budgeting, while economic costs (including opportunity costs, productivity losses, transport and out-of-pocket expenditure by patients) will determine cost-effectiveness and prioritization of resource allocations. For example, if an ART service package includes in-kind contributions such as food subsidies or other resources donated from external funding sources, these will influence future planning and sustainability. Ignoring such external assistance would distort the picture of overall costs and incentives structures in which an ART program operates.
There is a paucity of information about the delivery unit costs of ART and PMTCT in different HIV/AIDS programs, particularly in low-income countries. Future evaluations of program-level ART and PMTCT unit costs will benefit from international guidance on standardized expenditure definitions and categories, standardized formats for specifying ARV regimen mixes and laboratory testing practices (including type of tests and frequency) and for human resource disaggregation (facility-level vs. above-facility and program-level); as well as standardized service unit denominators (possibly including a component of service quality or of patient retention). The large differences in ART unit costs observed in settings with similar epidemiologic and economic characteristics deserve additional assessments focusing on cost determinants and opportunities for efficiency gain in program implementation and scale-up. To scale-up ART and PMTCT to universal access globally, innovative options are needed to contain costs while maintaining or improving quality and health gain.
We thank Daniel Acuña, who conducted the initial bibliographic search, as well as Lazarus Muchabaiwa and Jesse Kigozi for their research assistance. We acknowledge Sergio Bautista, Lisa DeMaria, Steven Forsythe, Lori Bollinger, Megan O’Brien and various participants at the first Latin America & the Caribbean Conference on Global Health in Cuernavaca, Mexico and at the XVIII International AIDS Conference in Vienna, Austria for helpful comments. The research was partially funded by the Global Fund to fight AIDS, Tuberculosis and Malaria (PO#2008301) through INSP/Consortium for Research on HIV/AIDS and Tuberculosis (CISIDAT1). Additional funding for Omar Galárraga was provided by U.S. National Institutes of Health (NIH)/Fogarty International Center (K01-TW008016-02) through the Institute of Business and Economic Research (IBER) at the University of California, Berkeley. The opinions expressed in the paper do not reflect the views of any of the funding or the other organizations that supported or facilitated the study.
1CISIDAT (www.cisidat.org.mx): Consortium for HIV/AIDS and Tuberculosis Research is a non-profit organization to support research in various academic and health care institutions in Mexico, among them the National Institute of Public Health (INSP).
The authors are solely responsible for the contents; they report no conflicts of interest.