TB Trade-Offs

This is a joint post with Kate McQueston.

The Wall Street Journal recently reported on a case of extensively drug-resistant tuberculosis (XDR-TB) found in a man who had traveled through 13 countries, and was stopped when attempting to enter the United States. This story – and others like it – make the headlines because both XDR-TB and multiple drug-resistant (MDR) TB are highly contagious and resistant to most treatment, leaving very limited (and often very toxic) options to patients who develop the disease. 

While scary, XDR-TB is relatively uncommon compared to other forms of the bacteria. TB infections totaled 8.7 million annually in 2011— and of this total, MDR-TB makes up 630,000 of total TB cases and  XDR-TB accounts for 25,000.  

Still, the costs associated with the treatment of MDR and XDR-TB are rising – treating one patient with MDR-TB medicines is equivalent to the costs of treating 200 patients with susceptible TB (that is, TB that responds to first-line treatment if taken properly.)

Yet despite higher costs and relatively low rates, most international agencies have made MDR-TB a priority. Dr. Margaret Chan, Director of WHO, has emphasized the need the scale up responses to MDR-TB. In 2011, the TB Global Drug Facility (a global mechanism that purchases TB drugs) spent $85.3 million purchasing drugs for MDR-TB for 19,605 patients, compared to $56.5 million for first-line drugs for over 2,000,000 patients.  As far as we can tell, the Global Fund (which provides almost 90% of international funding for tuberculosis) spends significant amounts on second-line treatments as well. The Fund’s Round 9 spending to date on second-line TB treatments accounted for 88% of total spending on tuberculosis medicines. This is an increase from the previous round (Round 8), where second line TB treatments accounted for 74% of total spending on TB medicines. As a caveat, the information available in the public PQR only gives us a partial picture how Global Fund disbursements are spent— only 11% and 21% of total TB grant disbursements for Rounds 8 and 9 respectively are recorded in the database.

Seeing most TB medicines spending go to MDR-TB makes sense if low-income countries are themselves covering the relatively lower costs of first-line treatment. However, total spending on TB by low-income countries is modest, and funding gaps remain large (today, WHO and the Global Fund estimated a US$ 600 million funding gap for susceptible TB, mostly in Africa). And while the largest share of total country funding used for the diagnosis of TB and treatment has traditionally been for first-line drugs, funding for the diagnosis and treatment of MDR-TB has been increasing in-country as well and is now estimated to exceed US$ 0.7 billion in 2013. In lower-middle income countries, total costs for second-line TB drugs now surpass spending on first line regimens. 

Total cost and unit cost of first- and second-line anti-TB drugs in 99 countries, 2009–2013, by income group

Source: here.

So the question is whether MDR-TB spending is displacing spending –and effort – from the adequate detection and treatment of susceptible TB, that –if done well – could actually prevent further MDR cases.  Comparisons of the number of cases notified and estimated TB incidence rates in WHO’s latest TB report suggests that high-burden countries are improving notification over time but large gaps remain in countries that are spending a chunk of external money on MDR (India, Pakistan, South Africa).  Further, first-line treatment success in high-burden settings is still problematic (Russia, South Africa).

Without economic modeling, it’s hard to say what mix of TB interventions in a given country will get us most quickly to Stop TB’s goal of a dramatically reduced global burden of TB in that country. Given that most TB spending in low-income countries is externally funded, is the current allocation (which seems to favor MDR-TB) the fastest way to reduce TB-related disease and disability? Would the optimal allocation between susceptible and MDR TB differ depending on whether you take a global or national perspective?

A new WHO/Global Fund TB factsheet announced that the Global Fund’s new funding model will prioritize the financial needs of low-income countries and their TB burden. And later in the month, StopTB is expected to release “investment framework” guidance to Global Fund applicants. Will we see recommendations on how to maximize impact on TB burden given a budget constraint? And if so, from whose perspective?