The South African Tuberculosis Care Cascade: Estimated Losses and Methodological Challenges

Abstract

Background: While tuberculosis incidence and mortality are declining in South Africa, meeting the goals of the End TB Strategy requires an invigorated programmatic response informed by accurate data. Enumerating the losses at each step in the care cascade enables appropriate targeting of interventions and resources.

Methods: We estimated the tuberculosis burden; the number and proportion of individuals with tuberculosis who accessed tests, had tuberculosis diagnosed, initiated treatment, and successfully completed treatment for all tuberculosis cases, for those with drug-susceptible tuberculosis (including human immunodeficiency virus (HIV)-coinfected cases) and rifampicin-resistant tuberculosis. Estimates were derived from national electronic tuberculosis register data, laboratory data, and published studies.

Results: The overall tuberculosis burden was estimated to be 532005 cases (range, 333760-764480 cases), with successful completion of treatment in 53% of cases. Losses occurred at multiple steps: 5% at test access, 13% at diagnosis, 12% at treatment initiation, and 17% at successful treatment completion. Overall losses were similar among all drug-susceptible cases and those with HIV coinfection (54% and 52%, respectively, successfully completed treatment). Losses were substantially higher among rifampicin- resistant cases, with only 22% successfully completing treatment.

Conclusion: Although the vast majority of individuals with tuberculosis engaged the public health system, just over half were successfully treated. Urgent efforts are required to improve implementation of existing policies and protocols to close gaps in tuberculosis diagnosis, treatment initiation, and successful treatment completion.

Keywords: Tuberculosis; care cascade; case-finding; continuum of care; initial loss to follow-up; treatment success.

Figure 1.

Estimated tuberculosis incidence and mortality in South Africa and projected sustainable development goals and End TB Strategy targets. Data on the estimated tuberculosis incidence rates and mortality for 2000 to 2015 are from the revised time series analysis of global tuberculosis burden published by the World Health Organization in 2016 [4]. Projected figures for 2030–2035 are based on targets relative to the 2015 estimates and assume a straight-line decline in tuberculosis incidence rates and mortality in this period.

Figure 2.

Approach to estimating the number of cases at each step in the tuberculosis care cascade. Abbreviations: DS, drug susceptible; HIV, human immunodeficiency virus; RIF-R, rifampicin resistant; WHO, World Health Organization.

Figure 3.

Care cascade for all patients with tuberculosis. This cascade includes patients with drug-susceptible tuberculosis and with all types of rifampicin-resistant tuberculosis. The wide confidence interval for the tuberculosis burden reflects the World Health Organisation incidence estimates for South Africa, which are based on case notification data and expert opinion on case detection gaps. The proportion at each step of the cascade is expressed in relation to the estimated burden.

Figure 4.

Care cascade for patients with drug-susceptible (DS) tuberculosis. The proportion at each step of the cascade is expressed in relation to the estimated burden.

Figure 5.

Care cascade for human immunodeficiency virus (HIV) co-infected patients with drug-susceptible (DS) tuberculosis. The proportion at each step of the cascade is expressed in relation to the estimated burden.

Figure 6.

Care cascade for patients with rifampicin-resistant (RIF-R) tuberculosis. The RIF-R tuberculosis burden has a wide confidence interval, reflecting a multiplier effect when both the confidence intervals for the tuberculosis burden for all patients (derived from World Health Organization incidence estimates) and the proportion with RIF-R tuberculosis (from the national drug-resistant tuberculosis prevalence survey) are taken into account. The cascade reflects all patients with RIF-R tuberculosis (including monoresistant, multidrug-resistant, pre–extensively drug-resistant, and extensively drug-resistant tuberculosis). The proportion at each step of the cascade is expressed in relation to the estimated burden.