Measuring socio-economic data in tuberculosis prevalence surveys

Is neglect of self-clearance biassing TB vaccine impact estimates?

Background

Mathematical modelling has been used extensively to estimate the potential impact of new tuberculosis vaccines, with the majority of existing models assuming that individuals with Mycobacterium tuberculosis (Mtb) infection remain at lifelong risk of tuberculosis disease. Recent research provides evidence that self-clearance of Mtb infection may be common, which may affect the potential impact of new vaccines that only take in infected or uninfected individuals. We explored how the inclusion of self-clearance in models of tuberculosis affects the estimates of vaccine impact in China and India.

Methods

For both countries, we calibrated a tuberculosis model to a scenario without self-clearance and to various scenarios with self-clearance. To account for the current uncertainty in self-clearance properties, we varied the rate of self-clearance, and the level of protection against reinfection in self-cleared individuals. We introduced potential new vaccines in 2025, exploring vaccines that work in uninfected or infected individuals only, or that are effective regardless of infection status, and modelling scenarios with different levels of vaccine efficacy in self-cleared individuals. We then estimated the relative incidence reduction in 2050 for each vaccine compared to the no vaccination scenario.

Findings

The inclusion of self-clearance increased the estimated relative reductions in incidence in 2050 for vaccines effective only in uninfected individuals, by a maximum of 12% in China and 8% in India. The inclusion of self-clearance increased the estimated impact of vaccines only effective in infected individuals in some scenarios and decreased it in others, by a maximum of 14% in China and 15% in India. As would be expected, the inclusion of self-clearance had minimal impact on estimated reductions in incidence for vaccines that work regardless of infection status.

Interpretations

Our work suggests that the neglect of self-clearance in mathematical models of tuberculosis vaccines does not result in substantially biased estimates of tuberculosis vaccine impact. It may, however, mean that we are slightly underestimating the relative advantages of vaccines that work in uninfected individuals only compared to those that work in infected individuals.

Asset and consumption gradient of health estimates in India: Implications for survey and public health research

The wealth index based on household assets and amenities is been increasingly used to explain economic variations of health outcomes in the developing countries. While the variables used to compute the wealth index are easy to collect and time- and cost-effective, the wealth index tends to have an urban bias, uses arbitrary weighting, does not provide per capita measures and is a poor measure of inequality. We used micro data from two of the large-scale population-based surveys, the Longitudinal Ageing Study in India, 2017–18 and the India Human Development Survey, 2011–12 that covered over 42,000 households each and collected data on household consumption, assets and amenities in India. We examined the variations and inequality in health estimates by consumption per capita and asset-based measures in India. Descriptive statistics, logistic regression model, concentration index, and concentration curve were used in the analyses.

We found a weak association between monthly per capita consumption expenditure (MPCE) and wealth index in both the surveys. Some of the health conditions such as hypertension, cataract, refractive error, and diabetes tended to be underestimated in the bottom 40% of the population when economic well-being was measured using the wealth index compared to consumption. Socio-economic inequality in health outcome, inpatient and outpatient health services were underestimated when measured using the wealth index than when measured using MPCE.

We conclude that economic gradients of health by consumption and wealth index are inconsistent and that per capita consumption predicts health estimates better than the wealth index. It is recommended that public health research using population-based surveys that provide data on consumption and wealth index use per capita consumption to explain economic variations in health and health care utilization. We also suggest that the future rounds of the health surveys of National Sample Survey and the National Family and Health Surveys include an abridged version of the consumption schedule to predict better economic variations in health and health care utilization in India.

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Wealth index has been increasingly used to explain economic variations in health outcomes in India.

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Association between monthly per capita consumption expenditure and wealth index is weak.

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Health estimates by consumption and wealth index are not consistent in India.

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Some of the measured health conditions are underestimated for the poor when economic well-being was measured using the wealth index compared to consumption.

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Socio-economic inequality in health outcome, inpatient and outpatient health services were underestimated when measured using the wealth index compared to consumption.

A comprehensive assessment of universal health coverage in 111 countries: a retrospective observational study

BACKGROUND

The goal of universal health coverage (UHC) requires that everyone receive needed health services, and that families who get needed services do not suffer undue financial hardship. Tracking progress towards UHC requires measurement of both these dimensions, and a way of trading them off against one another.

METHODS

We measured service coverage by a weighted geometric average of four prevention indicators (antenatal care, full immunisation, and screening for breast and cervical cancers) and four treatment indicators (skilled birth attendance, inpatient admission, and treatment for acute respiratory infection and diarrhoea), financial protection by the incidence of catastrophic health expenditures (those exceeding 10% of household consumption or income), and a country's UHC performance as a geometric average of the service coverage index and the complement of the incidence of catastrophic expenditures. Where possible, we adjusted service coverage for inequality, penalising countries with a high level of inequality. The bulk of data used in this study were from the World Bank's Health Equity and Financial Protection Indicators database (2019 version), comprising data from household surveys. Gaps in the data were supplemented with other survey data and (where necessary) non-survey data from other sources (administrative, modelled, and imputed data).

FINDINGS

A low incidence of catastrophic expenses sometimes reflects low service coverage (often in low-income countries) but sometimes occurs despite high service coverage (often in high-income countries). At a given level of service coverage, financial protection also varies. UHC index scores are generally higher in higher-income countries, but there are variations within income groups. Adjusting the UHC index for inequality in service coverage makes little difference in some countries, but reduces it by more than 10% in others. Seven of the 12 countries for which we were able to produce trend data have increased their UHC index over time (with the greatest average yearly increases seen in Ghana [1·43%], Indonesia [1·85%], and Vietnam [2·26%]), mostly by improving both financial protection and service coverage. Some increased their UHC index, despite reductions in financial protection, by substantially increasing their service coverage. The UHC index decreased in five of 12 countries with trend data, mostly because financial protection worsened with stagnant or declining service coverage. Our UHC indicators (except inpatient admissions) are significantly and positively associated with GDP per capita, and most are correlated with the share of health spending channelled through social health insurance and government schemes. However, associations of our UHC indicators with the share of GDP spent on health and the shares of health spending channelled through non-profit and private insurance are ambiguous.

INTERPRETATION

Progress towards UHC can be tracked using an index that captures both service coverage and financial protection. Although per-capita income is a good predictor of a country's UHC index score, some countries perform better than others in the same income group or even in the income group above their own. Strong UHC performance is correlated with the share of a country's health budget that is channelled through government and social health insurance schemes.

FUNDING

None.

Drug targets exploited in Mycobacterium tuberculosis: Pitfalls and promises on the horizon

Tuberculosis is an ever evolving infectious disease that still claims about 1.8 million human lives each year around the globe. Although modern chemotherapy has played a pivotal role in combating TB, the increasing emergence of drug-resistant TB aligned with HIV pandemic threaten its control. This highlights both the need to understand how our current drugs work and the need to develop new and more effective drugs. TB drug discovery is revisiting the clinically validated drug targets in Mycobacterium tuberculosis using whole-cell phenotypic assays in search of better therapeutic scaffolds. Herein, we review the promises of current TB drug regimens, major pitfalls faced, key drug targets exploited so far in M. tuberculosis along with the status of newly discovered drugs against drug resistant forms of TB. New antituberculosis regimens that use lesser number of drugs, require shorter duration of treatment, are equally effective against susceptible and resistant forms of disease, have acceptable toxicity profiles and behave friendly with anti-HIV regimens remains top most priority in TB drug discovery.

Socio-economic gradients in prevalent tuberculosis in Zambia and the Western Cape of South Africa

Objective

To describe the associations between socio‐economic position and prevalent tuberculosis in the 2010 ZAMSTAR Tuberculosis Prevalence Survey, one of the first large tuberculosis prevalence surveys in Southern Africa in the HIV era.

Methods

The main analyses used data on 34 446 individuals in Zambia and 30 017 individuals in South Africa with evaluable tuberculosis culture results. Logistic regression was used to estimate adjusted odds ratios for prevalent TB by two measures of socio‐economic position: household wealth, derived from data on assets using principal components analysis, and individual educational attainment. Mediation analysis was used to evaluate potential mechanisms for the observed social gradients.

Results

The quartile with highest household wealth index in Zambia and South Africa had, respectively, 0.55 (95% CI 0.33–0.92) times and 0.70 (95% CI 0.54–0.93) times the adjusted odds of prevalent TB of the bottom quartile. College or university‐educated individuals in Zambia and South Africa had, respectively, 0.25 (95% CI 0.12–0.54) and 0.42 (95% CI 0.25–0.70) times the adjusted odds of prevalent TB of individuals who had received only primary education. We found little evidence that these associations were mediated via several key proximal risk factors for TB, including HIV status.

Conclusion

These data suggest that social determinants of TB remain important even in the context of generalised HIV epidemics.

The epidemiological advantage of preferential targeting of tuberculosis control at the poor

Tuberculosis (TB) remains disproportionately concentrated among the poor, yet known determinants of TB reactivation may fail to explain observed disparities in disease rates according to wealth. Reviewing data on TB disparities in India and the wealth distribution of known TB risk factors, we describe how social mixing patterns could be contributing to TB disparities. Wealth-assortative mixing, whereby individuals are more likely to be in contact with others from similar socio-economic backgrounds, amplifies smaller differences in risk of TB, resulting in large population-level disparities. As disparities and assortativeness increase, TB becomes more difficult to control, an effect that is obscured by looking at population averages of epidemiological parameters, such as case detection rates. We illustrate how TB control efforts may benefit from preferential targeting toward the poor. In India, an equivalent-scale intervention could have a substantially greater impact if targeted at those living below the poverty line than with a population-wide strategy. In addition to potential efficiencies in targeting higher-risk populations, TB control efforts would lead to a greater reduction in secondary TB cases per primary case diagnosed if they were preferentially targeted at the poor. We highlight the need to collect programmatic data on TB disparities and explicitly incorporate equity considerations into TB control plans.

Care seeking in tuberculosis: results from a countrywide cluster randomised survey in Bangladesh

OBJECTIVES

To explore systematically the care seeking trajectories of tuberculosis (TB) cases up to four subsequent places of care and to assess the type of services provided at each place.

METHODS

TB cases detected actively during the 2007-2009 national TB prevalence survey and passively under the routine programme in the same period were interviewed by administering a standardised questionnaire. Care seeking and services provided up to four subsequent points were explored. Care seeking was further explored by categorising the providers into formal, informal and 'self-care' groups.

RESULTS

A total of 273 TB cases were included in this study, of which 33 (12%) were detected during the survey and 240 (88%) from the TB registers. Out of the 118 passively detected cases who first sought care from an informal provider, 52 (44.1%) remained in the informal sector at the second point of care. Similarly, out of the 52, 17 (32.7%) and out of the 17, 5 (29.4%) remained in the informal sector at the third and fourth subsequent points of care, respectively. All the 33 actively detected cases had 'self-care' at the first point, and 27 (81.8%) remained with 'self-care' up to the fourth point of care. Prescribing drugs (59-99%) was the major type of care provided by the formal and informal care providers at each point and was limited to the non-existent practice of investigation or referrals.

CONCLUSIONS

Free TB services are still underutilised by TB cases and informal caregivers remained the major care providers for such cases in Bangladesh. In order to improve case detection, it is necessary that the National Tuberculosis Programme immediately takes effective initiatives to engage all types of care providers, particularly informal providers who are the first point of care for the majority of the TB suspects.

Prevalence of self-reported tuberculosis, knowledge about tuberculosis transmission and its determinants among adults in India: results from a nation-wide cross-sectional household survey

Background

Knowledge about symptoms and transmission of tuberculosis determines health seeking behavior and helps in prevention of tuberculosis transmission in the community. Such data is useful for policy makers to formulate information, education and communication strategies for tuberculosis control.

Methods

A secondary data analysis of India demographic and health survey, 2005/6 was carried out. Questions about self-reported tuberculosis, transmission and curability of tuberculosis were analysed. Correct knowledge (without misconceptions) about tuberculosis transmission was used as a dependant variable and the explanatory variables tested were: demographic data, education, wealth quintiles, frequency of exposure to media and the curability of tuberculosis. Determinants of correct knowledge without misconceptions were tested by univariate and multivariate analyses using national weighting factor to adjust for complex sampling design.

Results

A total of 109,070 households (response rate of 93.5%) and 198,718 participants (response rate of 91.6%) completed the survey. The samples of men and women interviewed were 74,360 and 124,358 respectively. Prevalence rate of self-reported tuberculosis was 445 per 100,000 usual household residents and 4.60 per 1,000 participants. The number of respondents who had “heard of an illness called tuberculosis” was 177,423 (89.3%). Of these 47,487 (26.8%) participants did not know and 55.5% knew about the correct mode of tuberculosis transmission i.e. “Through the air when coughing or sneezing”. The common misconceptions about transmission were “Through food” (32.4%), “Sharing utensils” (18.2%), and “Touching a person with tuberculosis” (12.3%). Only 52,617 (29.7%) participants had correct knowledge without misconceptions. Being male (aOR 1.17, 95% CIs 1.14, 1.21), being a Hindu (aOR 1.20, 95% CIs 1.14, 1.26) or Muslim (aOR 1.26, 95% CIs 1.18, 1.34), listening to radio (aOR 1.08, 95% CIs 1.04, 1.13) and “Tuberculosis can be cured” (aOR 1.47, 95% CIs 1.41, 1.53) were associated with correct knowledge without misconceptions.

Conclusions

Knowledge about tuberculosis transmission is very poor and misconceptions still exist. Among the traditional mass media, the frequency of listening to radio was associated with correct knowledge about tuberculosis transmission. Strategies to deliver information, education and communication campaigns could be improved.

Socio economic position in TB prevalence and access to services: results from a population prevalence survey and a facility-based survey in Bangladesh

BACKGROUND

In Bangladesh DOTS has been provided free of charge since 1993, yet information on access to TB services by different population group is not well documented. The objective of this study was to assess and compare the socio economic position (SEP) of actively detected cases from the community and the cases being routinely detected under National Tuberculosis Control Programme (NTP) in Bangladesh.

METHODS AND FINDINGS

SEP was assessed by validated asset item for each of the 21,427 households included in the national tuberculosis prevalence survey 2007-2009. A principal component analysis generated household scores and categorized in quartiles. The distribution of 33 actively identified cases was compared with the 240 NTP cases over the identical SEP quartiles to evaluate access to TB services by different groups of the population. The population prevalence of tuberculosis was 5 times higher in the lowest quartiles of population (95.4, 95% CI: 48.0-189.7) to highest quartile population (19.5, 95% CI: 6.9-55.0). Among the 33 cases detected during survey, 25 (75.8%) were from lower two quartiles, and the rest 8 (24.3%) were from upper two quartiles. Among TB cases detected passively under NTP, more than half of them 137 (57.1%) were from uppermost two quartiles, 98 (41%) from the second quartile, and 5 (2%) in the lowest quartile of the population. This distribution is not affected when adjusted for other factors or interactions among them.

CONCLUSIONS

The findings indicate that despite availability free of charge, DOTS is not equally accessed by the poorer sections of the population. However, these figures should be interpreted with caution since there is a need for additional studies that assess in-depth poverty indicators and its determinants in relation to access of the TB services provided in Bangladesh.

Screening strategies for tuberculosis prevalence surveys: the value of chest radiography and symptoms

Background

We conducted a tuberculosis (TB) prevalence survey and evaluated the screening methods used in our survey, to assess if screening in TB prevalence surveys could be simplified, and to assess the accuracy of screening algorithms that may be applicable for active case finding.

Methods

All participants with a positive screen on either a symptom questionnaire, chest radiography (CXR) and/or sputum smear microscopy submitted sputum for culture. HIV status was obtained from prevalent cases. We estimated the accuracy of modified screening strategies with bacteriologically confirmed TB as the gold standard, and compared these with other survey reports. We also assessed whether sequential rather than parallel application of symptom, CXR and HIV screening would substantially reduce the number of participants requiring CXR and/or sputum culture.

Results

Presence of any abnormality on CXR had 94% (95%CI 88–98) sensitivity (92% in HIV-infected and 100% in HIV-uninfected) and 73% (95%CI 68–77) specificity. Symptom screening combinations had significantly lower sensitivity than CXR except for ‘any TB symptom’ which had 90% (95%CI 84–95) sensitivity (96% in HIV-infected and 82% in HIV-uninfected) and 32% (95%CI 30–34) specificity. Smear microscopy did not yield additional suspects, thus the combined symptom/CXR screen applied in the survey had 100% (95%CI 97–100) sensitivity. Specificity was 65% (95%CI 61–68). Sequential application of first a symptom screen for ‘any symptom’, followed by CXR-evaluation and different suspect criteria depending on HIV status would result in the largest reduction of the need for CXR and sputum culture, approximately 36%, but would underestimate prevalence by 11%.

Conclusion

CXR screening alone had higher accuracy compared to symptom screening alone. Combined CXR and symptom screening had the highest sensitivity and remains important for suspect identification in TB prevalence surveys in settings where bacteriological sputum examination of all participants is not feasible.