Antiretroviral therapy and demand for HIV testing: Evidence from Zambia

Demand for self-tests: Evidence from a Becker-DeGroot-Marschak mechanism field experiment

Self-tests offer one approach for reducing frictions underlying low demand for preventive health inputs, yet there is little evidence on demand for self-tests. We used the Becker-DeGroot-Marschak mechanism-an incentive-compatible approach-to elicit exact willingness to pay (WTP) for HIV self-tests in a field experiment with 822 participants at 66 health clinics/pharmacies in Kenya. Our analysis reveals substantial demand at low prices and highly elastic demand at a wide range of prices above this range. We find few participants with nonpositive WTP. We examine correlates of WTP and discuss policy and research implications of our findings.

Does Medicare Coverage Improve Cancer Detection and Mortality Outcomes?

Medicare is a large government health insurance program in the United States that covers about 60 million people. This paper analyzes the effects of Medicare insurance on health for a group of people in urgent need of medical care: people with cancer. We used a regression discontinuity design to assess impacts of near-universal Medicare insurance at age 65 on cancer detection and outcomes, using population-based cancer registries and vital statistics data. Our analysis focused on the three tumor sites for which screening is recommended both before and after age 65: breast, colorectal, and lung cancer. At age 65, cancer detection increased by 72 per 100,000 population among women and 33 per 100,000 population among men; cancer mortality also decreased by nine per 100,000 population for women but did not significantly change for men. In a placebo check, we found no comparable changes at age 65 in Canada. This study provides the first evidence to our knowledge that near-universal access to Medicare at age 65 is associated with improvements in population-level cancer mortality.

Bridging the Efficacy-Effectiveness Gap in HIV Programs: Lessons From Economics

BACKGROUND

Bridging the efficacy-effectiveness gap in HIV prevention and treatment requires policies that account for human behavior.

SETTING

Worldwide.

METHODS

We conducted a narrative review of the literature on HIV in the field of economics, identified common themes within the literature, and identified lessons for implementation science.

RESULTS

The reviewed studies illustrate how behaviors are shaped by perceived costs and benefits across a wide range of health and nonhealth domains, how structural constraints shape decision-making, how information interventions can still be effective in the epidemic's fourth decade, and how lessons from behavioral economics can be used to improve intervention effectiveness.

CONCLUSION

Economics provides theoretical insights and empirical methods that can guide HIV implementation science.

Cost-effectiveness and budget impact of immediate antiretroviral therapy initiation for treatment of HIV infection in Côte d'Ivoire: A model-based analysis

Introduction

The Temprano and START trials provided evidence to support early ART initiation recommendations. We projected long-term clinical and economic outcomes of immediate ART initiation in Côte d’Ivoire.

Methods

We used a mathematical model to compare three potential ART initiation criteria: 1) CD4 <350/μL (ART<350/μL); 2) CD4 <500/μL (ART<500/μL); and 3) ART at presentation (Immediate ART). Outcomes from the model included life expectancy, 10-year medical resource use, incremental cost-effectiveness ratios (ICERs) in $/year of life saved (YLS), and 5-year budget impact. We simulated people with HIV (PWH) in care (mean CD4: 259/μL, SD 198/μL) and transmitted cases. Key input parameters to the analysis included first-line ART efficacy (80% suppression at 6 months) and ART cost ($90/person-year). We assessed cost-effectiveness relative to Côte d’Ivoire’s 2017 per capita annual gross domestic product ($1,600).

Results

Immediate ART increased life expectancy by 0.34 years compared to ART<350/μL and 0.17 years compared to ART<500/μL. Immediate ART resulted in 4,500 fewer 10-year transmissions per 170,000 PWH compared to ART<350/μL. In cost-effectiveness analysis, Immediate ART had a 10-year ICER of $680/YLS compared to ART<350/μL, ranging from cost-saving to an ICER of $1,440/YLS as transmission rates varied. ART<500/μL was “dominated” (an inefficient use of resources), compared with Immediate ART. Immediate ART increased the 5-year HIV care budget from $801.9M to $812.6M compared to ART<350/μL.

Conclusions

In Côte d’Ivoire, immediate compared to later ART initiation will increase life expectancy, decrease HIV transmission, and be cost-effective over the long-term, with modest budget impact. Immediate ART initiation is an appropriate, high-value standard of care in Côte d’Ivoire and similar settings.

Altruism in preventive health behavior: At-scale evidence from the HIV/AIDS pandemic

Preventive behavior with regards to disease transmission offers a promising context in which to provide empirical evidence on altruism in human populations. I examine the association between HIV status, own knowledge about status, and preventive health behavior using household survey data from over 200,000 individuals in 25 sub-Saharan African countries. I find that individuals who are HIV positive and have taken a standard HIV test are much more likely to engage in efforts to prevent HIV transmission than are individuals who are HIV negative and have taken a standard HIV test. Moreover, this difference is greater than the difference between HIV positives and HIV negatives for individuals who have not taken a standard HIV test. Consistent with an altruistic motivation, this double-difference is larger for individuals who are married than for individuals who are not married. These results appear to be the first evidence on the change in risky sexual behavior associated with HIV testing at scale and are consistent with altruism dominating any self-interested response to HIV testing.

Estimating the real-world effects of expanding antiretroviral treatment eligibility: Evidence from a regression discontinuity analysis in Zambia

BACKGROUND

Although randomized trials have established the clinical efficacy of treating all persons living with HIV (PLWHs), expanding treatment eligibility in the real world may have additional behavioral effects (e.g., changes in retention) or lead to unintended consequences (e.g., crowding out sicker patients owing to increased patient volume). Using a regression discontinuity design, we sought to assess the effects of a previous change to Zambia's HIV treatment guidelines increasing the threshold for treatment eligibility from 350 to 500 cells/μL to anticipate effects of current global efforts to treat all PLWHs.

METHODS AND FINDINGS

We analyzed antiretroviral therapy (ART)-naïve adults who newly enrolled in HIV care in a network of 64 clinics operated by the Zambian Ministry of Health and supported by the Centre for Infectious Disease Research in Zambia (CIDRZ). Patients were restricted to those enrolling in a narrow window around the April 1, 2014 change to Zambian HIV treatment guidelines that raised the CD4 threshold for treatment from 350 to 500 cells/μL (i.e., August 1, 2013, to November 1, 2014). Clinical and sociodemographic data were obtained from an electronic medical record system used in routine care. We used a regression discontinuity design to estimate the effects of this change in treatment eligibility on ART initiation within 3 months of enrollment, retention in care at 6 months (defined as clinic attendance between 3 and 9 months after enrollment), and a composite of both ART initiation by 3 months and retention in care at 6 months in all new enrollees. We also performed an instrumental variable (IV) analysis to quantify the effect of actually initiating ART because of this guideline change on retention. Overall, 34,857 ART-naïve patients (39.1% male, median age 34 years [IQR 28-41], median CD4 268 cells/μL [IQR 134-430]) newly enrolled in HIV care during this period; 23,036 were analyzed after excluding patients around the threshold to allow for clinic-to-clinic variations in actual guideline uptake. In all newly enrolling patients, expanding the CD4 threshold for treatment from 350 to 500 cells/μL was associated with a 13.6% absolute increase in ART initiation within 3 months of enrollment (95% CI, 11.1%-16.2%), a 4.1% absolute increase in retention at 6 months (95% CI, 1.6%-6.7%), and a 10.8% absolute increase in the percentage of patients who initiated ART by 3 months and were retained at six months (95% CI, 8.1%-13.5%). These effects were greatest in patients who would have become newly eligible for ART with the change in guidelines: a 43.7% increase in ART initiation by 3 months (95% CI, 37.5%-49.9%), 13.6% increase in retention at six months (95% CI, 7.3%-20.0%), and a 35.5% increase in the percentage of patients on ART at 3 months and still in care at 6 months [95% CI, 29.2%-41.9%). We did not observe decreases in ART initiation or retention in patients not directly targeted by the guideline change. An IV analysis found that initiating ART in response to the guideline change led to a 37.9% (95% CI, 28.8%-46.9%) absolute increase in retention in care. Limitations of this study include uncertain generalizability under newer models of care, lack of laboratory data (e.g., viral load), inability to account for earlier stages in the HIV care cascade (e.g., HIV testing and linkage), and potential for misclassification of eligibility status or outcome.

CONCLUSIONS

In this study, guidelines raising the CD4 threshold for treatment from 350 to 500 cells/μL were associated with a rapid rise in ART initiation as well as enhanced retention among newly treatment-eligible patients, without negatively impacting patients with lower CD4 levels. These data suggest that health systems in Zambia and other high-prevalence settings could substantially enhance engagement even among those with high CD4 levels (i.e., above 500 cells/μL) by expanding treatment without undermining existing care standards.

Does integrating AIDS treatment with food assistance affect labor supply? Evidence from Zambia

In low income settings, food assistance is increasingly becoming part of AIDS treatment and care programs with the aim of improving adherence to AIDS treatment, enhancing household food security and strengthening economic wellbeing. Yet, evidence of its economic impact is sparse. This paper uses primary data to examine the short term impact of a food assistance program on labor supply as measured by the hours worked, labor market participation rates and transitions to employment within HIV/AIDS affected households in Zambia. We find that food assistance is generally a labor supply disincentive to HIV-infected patients receiving treatment as it reduced their hours worked by up to 54%, transitions to employment by up to 70% and also reduced the labor market participation rates of male patients by 72%. Among non-infected adult family members, there were no significant effects on labor market participation. However, propensity score estimates show that food assistance generally increased the intensity of work by males regardless of the length of AIDS treatment, but for females there was a disincentive effect that disappeared when the patient had spent a longer time on AIDS treatment and was therefore healthier and less likely to be cared for. These findings suggest that food assistance can inadvertently reduce the labor supply of HIV-infected individuals, but this is compensated for by the increased labor supply among other family members.

Causal effects of HIV on employment status in low-income settings

This paper estimates the causal impact of being HIV positive on individual employment status using a recursive bivariate probit with male circumcision as the instrument to overcome the endogeneity arising from simultaneity bias. The results show that being HIV positive reduces the probability of being employed by 5 percentage points among males in Uganda. The effect is greater for individuals employed in manual labor than non-manual labor. When limiting the sample to mainly individuals employed in subsistence agriculture, we find a 4 percentage point reduction in the likelihood of employment, suggesting that the effect occurs primarily through reductions in labor supply as opposed to demand. This is supported by additional analysis using univariate probit regressions to assess the association between different levels of HIV illness (as measured by CD4 cell count) and the likelihood of employment. The magnitude of the association increases as CD4 cell count decreases. Having a CD4 cell count of 200permm³ or below is associated with a 9 percentage point reduction in employment compared to individuals with CD4 cell counts above 200permm³.

Quasi-experiments to establish causal effects of HIV care and treatment and to improve the cascade of care

PURPOSE OF REVIEW

Randomized, population-representative trials of clinical interventions are rare. Quasi-experiments have been used successfully to generate causal evidence on the cascade of HIV care in a broad range of real-world settings.

RECENT FINDINGS

Quasi-experiments exploit exogenous, or quasi-random, variation occurring naturally in the world or because of an administrative rule or policy change to estimate causal effects. Well designed quasi-experiments have greater internal validity than typical observational research designs. At the same time, quasi-experiments may also have potential for greater external validity than experiments and can be implemented when randomized clinical trials are infeasible or unethical. Quasi-experimental studies have established the causal effects of HIV testing and initiation of antiretroviral therapy on health, economic outcomes and sexual behaviors, as well as indirect effects on other community members. Recent quasi-experiments have evaluated specific interventions to improve patient performance in the cascade of care, providing causal evidence to optimize clinical management of HIV.

SUMMARY

Quasi-experiments have generated important data on the real-world impacts of HIV testing and treatment and on interventions to improve the cascade of care. With the growth in large-scale clinical and administrative data, quasi-experiments enable rigorous evaluation of policies implemented in real-world settings.