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Post-2015 Consensus: Health Perspective - Tuberculosis, Vassall

Summary 

The economic case for investment in tuberculosis (TB) control is compelling; treatment is low cost and highly effective, and on average may give an individual in the middle of their productive life around 20 additional years of life, resulting in substantial economic and health return. But TB receives less than 4% of total development assistance for health. Over 9 million individuals fell ill with TB in 2013, and it remains a major cause of global mortality, with the annual number of deaths being estimated at 1·4 million. This is a substantial (and primarily preventable) proportion of the 53 million deaths occurring globally per year.

TB has two stages, latent infection and active TB. Over two billion people worldwide are latently infected, and 5% of those develop active TB within 18 months, with a further 5% risk of developing active TB over a lifetime. The risk of developing the active form increases substantially after HIV infection. Most TB responds well to standard drug treatment, but there were almost half a million cases of multi-drug resistant TB (MDR-TB) in 2013, with over 10% of these cases being extensively drug-resistant (XDR-TB) in some countries.

Between 1990 and 2010 there was a 38% reduction in the disease burden from TB (per 100,000 people) and the mortality rate had fallen by 45% by 2013. However, absolute numbers continue to rise, with 7.1 million cases among HIV-negative individuals. The post-2015 strategy aims to end the global TB epidemic, with targets to reduce TB deaths by 95% and new TB cases by 90% between 2015 and 2035, while ensuring no family is burdened with catastrophic expenses due to the disease. Although progress in the last two decades suggests that TB control is beginning to work, an effective response has been hampered by weak health systems, poverty and sub-optimal medical technologies.

TB can be difficult to diagnose and most programs rely on passive case finding. About 30% of all active TB cases go unrecognized. Providing preventative TB treatment in those populations with a high risk of developing active TB is recommended by the World Health Organisation (WHO). The treatment of drug susceptible TB involves delivering a standard low cost (around $21 per person for drugs only) regimen of TB treatment, usually for six months. The treatment of MDR-TB is far more complex, can take 24 months or longer and is also much less effective.

Despite the availability of screening, diagnostic and treatment technologies for TB, there remains substantial scope for improvement. Investment in new diagnostic and treatment technologies may both substantially improve the efficacy of TB control and help address some of the numerous health system and patient side barriers to deliver service.

Estimating one figure that summarises the overall cost-benefit of reaching the post-2015 targets is complex. This paper instead estimates weighted benefit cost ratios (BCRs) based on the relative population in need of each intervention in 2013. The cost-effectiveness of screening and treatment of latent TB in those with HIV is long established, and treatment of drug-susceptible TB is one of the most cost-effective components of a basic package of health care. Also, while diagnosing and treating MDR-TB may be more costly than treating drug-susceptible TB, it has still been found to be cost-effective.

Using figures from various studies, and a mixture of approaches for valuing disability adjusted life years (DALYs), we estimate that the current  BCR for the diagnosis and treatment of TB is likely to be somewhere in the range 11-192: 1 depending on the value of a DALY used. For countries adopting intensified case detection and treatment of latent TB for those living with HIV, the additional investment has a BCR of 6-47:1. For countries diagnosing and treating MDR-TB, the extra investment has a BCR of 0-5:1. These are likely to be conservative estimates, since they take little  account of transmission benefits, or welfare gains from reducing poverty or increasing equity. It is also assumed that there will be no new advances which shorten or improve the course of treatment. On the other hand, the analysis may underestimate the costs of strengthening and expanding health systems.

Overall, the weighted average benefit cost ratios for reducing TB deaths by 95% and TB incidence by 90% between 2015 and 2035 are between 16 (low DALY, 5% discount rate) to  82 (high DALY, 3% discount rate). The benefit will primarily accrue to the very poorest globally.