Has the DOTS strategy improved case finding or treatment success? An empirical assessment

Abstract

Background: Nearly fifteen years after the start of WHO's DOTS strategy, tuberculosis remains a major global health problem. Given the lack of empirical evidence that DOTS reduces tuberculosis burden, considerable debate has arisen about its place in the future of global tuberculosis control efforts. An independent evaluation of DOTS, one of the most widely-implemented and longest-running interventions in global health, is a prerequisite for meaningful improvements to tuberculosis control efforts, including WHO's new Stop TB Strategy. We investigate the impact of the expansion of the DOTS strategy on tuberculosis case finding and treatment success, using only empirical data.

Methods and findings: We study the effect of DOTS using time-series cross-sectional methods. We first estimate the impact of DOTS expansion on case detection, using reported case notification data and controlling for other determinants of change in notifications, including HIV prevalence, GDP, and country-specific effects. We then estimate the effect of DOTS expansion on treatment success. DOTS programme variables had no statistically significant impact on case detection in a wide range of models and specifications. DOTS population coverage had a significant effect on overall treatment success rates, such that countries with full DOTS coverage benefit from at least an 18% increase in treatment success (95% CI: 5-31%).

Conclusions: The DOTS technical package improved overall treatment success. By contrast, DOTS expansion had no effect on case detection. This finding is less optimistic than previous analyses. Better epidemiological and programme data would facilitate future monitoring and evaluation efforts.

Figure 1. Total smear-positive and smear-negative tuberculosis cases notified to WHO, 1980–2005

Figure 2. Tuberculosis cases reported to WHO in six of ten countries with known recent transitions to electronic case recording or reporting, 1980–2005

Figure 3. Smear-positive tuberculosis notifications, shown alongside DOTS coverage, 1995–2005; Figure 3a (top): Smear-positive tuberculosis notifications to WHO, as reported vs excluding countries with known transitions to electronic tuberculosis reporting (ETBR: Botswana, China, India, Indonesia, Korea, Lesotho, Namibia, Nepal, Philippines, South Africa), 1995–2005; Figure 3b (bottom): Percent of world population living in areas (e.g., districts, counties) implementing DOTS, 1995–2005

Figure 4. Median and 10–90th percentile range of treatment success rates for countries reporting DOTS and non-DOTS treatment outcomes, 1995–2004