Review 3: "The Effect of Conditional Cash Transfers on Tuberculosis Incidence and Mortality is Determined by Ethnoracial and Socioeconomic Factors: A Cohort Study of 54 Million Individuals in Brazil"

RR:C19 Evidence Scale rating by reviewer:

• Reliable. The main study claims are generally justified by its methods and data. The results and conclusions are likely to be similar to the hypothetical ideal study. There are some minor caveats or limitations, but they would/do not change the major claims of the study. The study provides sufficient strength of evidence on its own that its main claims should be considered actionable, with some room for future revision.

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Review: In the last three decades conditional cash transfers (CCT) have been one of the main ways of addressing social determinants of health from a public health perspective in Latin American Countries¹. The rationale behind a CCT lies in promoting certain health behaviours in 2 main areas: school and preventive health services attendance, the attainment of which conditions the cash transfer.

Based on the target population scope, we may postulate two categories of CCT policies: those broadly implemented at national level for vulnerable populations, such as “Oportunidades” in Mexico, “Programa Bolsa Familia” in Brazil or “Asignación Universal por Hijo” in Argentina, which could be broadly defined as “poverty relief” interventions and have proved to be effective at reducing different disease incidences such as low child birth weight², HIV³ and, like in Jesus et al., TB⁴. In this way, we can regard this CCT scheme as a primary prevention intervention, working through mechanisms such as better nutrition and less crowding conditions, among others. There is another type of CCT which could be called “specific CCT”, in the sense that resource transfers are earmarked to a certain disease. Beneficiaries are individuals already with the disease, and the main objective is targeted at improving treatment adherence, possibly through partial compensation of loss of income due to inability to work, especially in the context of precarious jobs, improved access to transportation (for healthcare consultations) and the availability of time to complete diagnostic studies or getting pharmacologic treatment. Conditionalities in these focused CCT programs may include following a strict calendar of regular checkups with health providers and, in the specific case of TB, treatment completion.

In their study, Jesus et al. evaluated a “generic preventive” CCT and not a “specific CCT”. The authors report a strong and robust effect of the BFP on decreasing both TB incidence and mortality rates, with a notable effect modification showing a marked gradient based on ethnoracial and socioeconomic conditions, showing greater effects among Indigenous, Black/pardo, and extremely poor populations. Although the inherent limitation of the quasi-experimental design prevents us from sustaining a direct causal relationship between the BFP and the reduction of the adverse TB outcomes (both incidence and mortality), the detailed description of the solid statistical analysis used allows for a strong argument in favour of that effect.

As mentioned, effect heterogeneity was explored for ethnicity, income, gender, age and education. In these subgroup analyses, DOT coverage was included as a confounding variable, meaning that BFP effectiveness was ascertained adjusting for DOT coverage. Klein et al. found that DOT strategy could work as a confounder but also as an effect-modifier, showing a greater effect of the CCT among patients under self-administered treatment than those under DOTS⁵. It would be very informative to see if relevant interaction between CCT and DOT strategy was also present in this study. Interventions that improve adherence to treatment also have the potential of reducing incidence since successful treatments mean less TB transmission at home, work, school or closed communities. 

Is there a choice to make among generic and more specific interventions for social support?

Possibly not. Both CCT strategies have their place in today’s policy toolkit as upstream interventions addressing structural poverty-related situations and diseases like TB. One could think of a broad net for millions of people living in poverty, and a targeted approach for thousands of TB patients who face many social barriers to completing therapy, complemented by availability of proactive primary care health services (i.e. Family Health Program) and reinforcement of treatment assistance and supervision strategies. 

A final word for praise to the authors on the work on database linkage. Having access to social policy, epidemic surveillance and death registry databases, the authors managed to assemble a multi-million cohort and (retrospectively) follow them up for long periods of time, without access to electronic health record data which, in low and middle income countries, are still widely unavailable.  The study presents data from an unprecedented large longitudinal dataset, combined with solid quasi-experimental evaluation methods, assessing the effects of a generic social support policy such as the BFP on TB outcomes, a disease long recognised as related to adverse socio-economic conditions. These important results apply to subgroups of beneficiaries usually underrepresented in cohort studies and randomised controlled trials and reveal important differential effects of the policy intervention in mitigating some of the socioeconomic conditions in general, and possibly on poverty related diseases like TB in particular.

References:

1. Sun S, Huang J, Hudson DL, Sherraden M. Cash Transfers and Health. Annu Rev Public Health. 2021 Apr 1;42:363-380

2. Siddiqi A, Rajaram A, Miller SP. Do cash transfer programmes yield better health in the first year of life? A systematic review linking low-income/middle-income and high-income contexts. Arch Dis Child. 2018 Oct;103(10):920-926

3. Guimarães NS, Magno L, de Paula AA, Silliman M, Anderle RVR, Rasella D, Macinko J, de Souza LE, Dourado I. The effects of cash transfer programmes on HIV/AIDS prevention and care outcomes: a systematic review and meta-analysis of intervention studies. Lancet HIV. 2023 Jun;10(6):e394-403.

4. Nery JS, Rodrigues LC, Rasella D, Aquino R, Barreira D, Torrens AW, Boccia D, Penna GO, Penna MLF, Barreto ML, Pereira SM. Effect of Brazil's conditional cash transfer programme on tuberculosis incidence. Int J Tuberc Lung Dis. 2017 Jul 1;21(7):790-796

5. Klein K, Bernachea MP, Irribarren S, Gibbons L, Chirico C, Rubinstein F. Evaluation of a social protection policy on tuberculosis treatment outcomes: A prospective cohort study. PLoS Med. 2019 Apr 30;16(4):e1002788