Chagas disease turns its back on the lab

Laurence Flevaud, MSF’s laboratory advisor, has coordinated a multicentre study to assess the efficacy of rapid diagnosis tests for Chagas disease. In view of the results of the study, Laurence tells us about the myths they have managed to break.

What are the results of the study and why are they important?

The study shows that we no longer have to invest so much in research & development (R&D) for Chagas diagnosis; the rapid tests available in the market are effective enough and their performance is good. This breaks many taboos about the disease. The “there-is-no-simple-diagnostic-test-for-Chagas-available” argument can no longer be used as an excuse for not treating the sick.

For the first time, an independent study proves that 6 out of the 11 rapid tests available in the market to diagnose Chagas are effective and work in America as well as in Europe and the Asia-Pacific area. The use of these rapid tests will enable us to diagnose Chagas not just in highly specialised labs. 

How did the idea to carry out this study come up?

The idea of the study stems from the shortcomings we have to face in our projects, mainly in rural areas in Bolivia and Paraguay, where there are no labs nearby. For instance, in Paraguay, we had to transport the blood samples needed to confirm the Chagas diagnosis at 45º using a cold chain; logistically it was a nightmare. In addition to covering our own needs, we knew that many more sick people would be able to benefit if the diagnosis was simplified.

In parallel, in 2010, the World Health Organization (WHO) approved a resolution urging to integrate Chagas diagnosis and treatment in primary and secondary health facilities; in order to do this,  simplifying diagnostics was a must, bearing in mind that in these health centres there is no lab - above all in most Latin American countries. Therefore, since 2010 we have been working with the WHO and institutions worldwide, for instance the US Center for Disease Control and Prevention (CDC), to implement the study.

What could be the impact of the study for Chagas patients?

We bring diagnosis and also treatment closer to them. For instance, a person going to a health centre for a rapid test would know in just a few minutes whether they were affected with Chagas and in need of treatment.

Right now, several conventional lab tests are needed to diagnose Chagas. One of them, the ELISA test, cannot be done individually; you need a minimum number of samples (between 50 and 100) to do the testing. The diagnosis may even be delayed up to six months and we know that during this time we lose many potential patients.

Moreover, as some of the organizations that determine the health policy of Chagas have participated in the study, we trust that there will soon be global changes. For instance, although the WHO recommends confirming Chagas diagnosis using two conventional lab tests, and a third one if there is a discrepancy, this recommendation will most probably change at the end of the year.

What else do we need in terms of Chagas diagnosis?

We are now in the second phase of the study, where we analyse the different rapid tests under field conditions and with different variables: considering several contexts, various prevalences and two strains of Triponosoma cruzi. All of this information will enable us to create better diagnostic algorithms per area – i.e. a rapid test may be very effective in highly prevalent areas in Bolivia, where we are fighting the cruzi2 parasite, while in Mexico, in areas where cruzi1 prevalence is low, we need to cross two rapid tests. We will also know which rapid test is better for Europe or the USA, for instance. Anyhow, we will have taken a big leap in the diagnosis of, and therefore in the fight against, Chagas.

However, there is no need to wait for these results to use rapid tests: they have been on the market for years and we now have scientific evidence of their efficacy. National Chagas programmes, ministries of health or the organisations working on Chagas already have enough information to use them. 

What more resources are needed to keep moving forward in the fight against Chagas?

Without any doubt, mid- to long-term research and development for Chagas should focus on getting a test of cure. With the methods we have now, confirming treatment efficacy in adolescents and adults may take decades. PCR (polymerase chain reaction) techniques, based on genetic information, can only be used within the framework of clinical trials to study the efficacy of new drugs.  

In the last few years we have already shown the benefits of treatment and how it helps to curb the disease, decreasing the risk of developing heart, digestive and neurological lesions. However, we still don’t have a test that within a reasonable timeframe enables us to tell the patient that they are cured.