We in the United States may not think about it much, but more than one billion people are affected by tropical diseases such as schistosomiasis and leprosy. These diseases cause chronic disability and death in countless adults and children.
Now Stanford researcher John Ioannidis, MD, DSc, chief of the Stanford Prevention Research Center, has published in the British Medical Journal an analysis of medical interventions for 16 tropical diseases. He and the first author of the study, Shanthi Kappagoda, MD, found that, for most, there is little reliable evidence for the efficacy of one intervention versus another. According to Ioannidis:
These 16 diseases have an enormous impact on health on a global level. More than a billion people are affected by them, and every year the disease burden from these diseases amounts to 57 million disability-adjusted life years. Although close to 1000 trials have been performed on different treatments for these diseases, they are are done one at a time and there is no coordination of the total research agenda that emerges.
The researchers conclude in the article:
Either a single trial or trials with fewer than 100 participants comprised the randomised evidence for first or second line treatments for Buruli ulcer, human African trypanosomiasis, American trypanosomiasis, cysticercosis, rabies, echinococcosis, New World cutaneous leishmaniasis, and each of the foodborne trematode infections. Among the 10 disease categories with more than 40 trials, five lacked sufficient head to head comparisons between first or second line treatments.
Studies like these are critically important to identifying knowledge gaps. They also highlight the role economics play in disease research. According to Ioannidis:
These are not diseases to make money from (most of the people affected are poor and live in poor countries), so the large majority of the clinical trials research is not done by the pharmaceutical industry. By analyzing the networks of the comparisons of all trials that have been performed to-date, we can identify what are the important comparisons that would need to be studied in future studies so as to cover the most essential knowledge gaps about how to best treat these incapacitating and deadly ailments.