We evaluated the costs incurred in each arm of the CIPRA HT-001 trial and compared the incremental cost and survival benefit of early versus standard ART in order to determine the cost-effectiveness of early ART over a maximum 3-y time horizon. Higher ART and associated nursing and pharmacist costs in the early ART group were partially offset by higher costs for HIV physician visits, other medications, CD4 cell counts, clinically indicated laboratory tests, and radiographs in the standard group.
These are the only data, to our knowledge, comparing the cost of early versus standard ART using data from a randomized trial that compared these two strategies. HIV treatment protocols, laboratory tests, and medication costs are similar to those in other resource-poor settings, particularly programs funded in part by US President's Emergency Plan for AIDS Relief (PEPFAR). Our findings are also generalizable to nontrial settings, as the patients in the CIPRA HT-001 trial received nearly identical medical services as nonstudy patients, with similar frequencies of physician and nurse contacts compared to those previously described for usual care at GHESKIO 
The WHO-CHOosing Interventions that are Cost Effective (CHOICE) Working Group designates interventions as cost-effective if the cost per disability-adjusted life year (DALY) averted is less than three times the country's per capita gross domestic product (GDP) and very cost-effective if the cost per DALY is less than one times the country's GDP per capita 
. Between and even below these thresholds, each country needs to consider what interventions to fund and how to obtain additional financial support to expand coverage. Although our analysis computes cost-effectiveness ratios in terms of YLS rather than using DALYs, the WHO threshold provides general guidance that has been used in other studies using YLS 
. In Haiti this threshold was US$2,355/YLS in 2009 
. The cost-effectiveness ratio of early versus standard ART was above this threshold if research-related tests were included (US$3,975/YLS), but below the threshold if research-related tests were excluded (US$2,050/YLS). More aggressive monitoring for anemia on zidovudine slightly increased the cost-effectiveness ratio, while substituting tenofovir for zidovudine or using a higher cost second-line ART regimen resulted in more substantial increases in the cost-effectiveness ratio. Recent trends, however, indicate that costs for tenofovir and second-line regimens are declining 
These cost-effectiveness ratios are highly conservative (biased against early ART), because they do not include the clinical benefits of earlier treatment that would continue beyond the maximum 3-y time horizon of our study. The median CD4 cell count at ART initiation was 280 cells/mm3
in the early group and 166 cells/mm3
in the standard group. Multiple studies have demonstrated that higher baseline CD4 cell counts are associated with improvements in immunologic recovery and lower long-term mortality on ART 
. In contrast, a significant proportion of patients who defer ART until the CD4 cell count drops below 200 cells/mm3
will fail to achieve a normal CD4 cell count and will experience a higher rate of morbidity and mortality from both AIDS- and non-AIDS–related diseases, even after 7 to 10 y of otherwise effective therapy 
. Additional benefits of earlier treatment that were not measured include averted cases of TB among contacts of the participants associated with the lower rate of active TB infection in the early group, and the reduction in HIV transmission with earlier initiation of ART 
Our study results are important for low- and middle-income countries to consider as they decide whether to adopt the new WHO guidelines. ART costs in the standard group were US$81 per person over the median follow-up time of 21 mo because, even through these participants did not initiate ART early, 39% of them subsequently had a CD4 cell count measurement ≤200 cells/mm3 or developed an AIDS-defining illness and initiated ART. ART costs in the early group were US$317 higher (US$398 per person), but these incremental ART costs were partly offset by savings in the cost of non-ART medications, CD4 cell counts, clinically indicated tests, and radiographs. In countries that have access to similar ART prices but have higher labor rates and a more developed hospital infrastructure, care cost savings might be greater.
To our knowledge, this is the first cost-effectiveness study of early versus deferred ART eligibility thresholds conducted alongside a prospective randomized trial. The trial was designed to minimize loss to follow-up in order to obtain valid study endpoints in both arms, and therefore does not take into account recent observations from South Africa that HIV-infected patients with a CD4 cell count above a threshold for ART initiation are much more likely to be lost to follow-up than those who can initiate treatment immediately 
. Patient adherence to medications and physician adherence to guidelines in a clinical trial setting may also differ from nontrial settings 
. Nevertheless, our findings are similar to published results from a computer simulation model of HIV disease in the medium term that conducted sensitivity analyses addressing these issues. Walensky et al. found that in South Africa, the incremental cost-effectiveness ratio for initiating ART at a threshold of 350 cells/mm3
was US$2,400/YLS compared with initiating ART at 250 cells/mm3
, when measured over a 5-y time horizon 
. In a study conducted in Morocco, initiating ART >200 cells/mm3
had a cost-effectiveness ratio that was nearly three times GDP per capita when measured over a 5-y time horizon 
. Although longer follow-up is not feasible in a clinical trial, several computer simulation results show that the cost-effectiveness of earlier ART is lower with a lifetime perspective: US$1,200/YLS and US$616/QALY in South Africa and US$1,530/YLS in India 
. The long-term cost-effectiveness of early versus standard ART in this study will depend on whether the early group continues to have a survival benefit after standard group patients have initiated ART and whether there are any differences in second-line ART initiation rates between the two groups in the future; these data are currently being collected.
Beyond the absence of long-term follow-up, our study has additional limitations. We report years of life saved because there are no data on disability or quality-of-life measures for patients with early HIV disease in Haiti. If we had, earlier treatment would likely have been even more cost-effective, because the quality of life benefit of avoiding the 18 additional cases of TB that occurred in the standard group would outweigh the small number of additional drug-related adverse events observed in the early group 
. The cost-effectiveness ratio was lower when we excluded research-related tests. We are confident on the basis of results of a large randomized trial 
and GHESKIO clinic data 
that clinical outcomes would have been unchanged in the absence of these tests. Although our study was conducted at one site, many of our findings will be generalizable to other resource-poor settings because we use similar treatment protocols. Our study only addresses relatively short-term costs, i.e., up to a maximum of 3 y. Follow-up data on patient survival, new treatment protocols (such as introduction of targeted HIV viral load monitoring) 
, and costs will allow us to address long-term economic outcomes.
There are substantial budget and logistical constraints to implementing earlier treatment, including ensuring priority access to ART for the sickest patients and not diverting resources away from identifying these patients and retaining them in care. Furthermore, the results of cost-effectiveness analyses should only be one element in the priority setting process in the face of budget constraints. On the other hand, the CIPRA HT-001 trial was stopped because earlier treatment substantially decreased mortality 
, and our economic analysis indicates that it can be cost-effective in resource-poor settings.
Initiating ART in HIV-infected adults with a CD4 cell count between 200 and 350 cells/mm3 in Haiti is cost-effective after excluding laboratory monitoring without clinical benefit. Financial and operational resources should be prioritized so that resource-poor countries are able to implement the new WHO guidelines, which recommend treatment for all HIV-infected patients with CD4 cell counts <350 cells/mm3.