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Neglected tropical diseases: survey and geometry of randomised evidence

BMJ 2012; 345 doi: (Published 22 October 2012) Cite this as: BMJ 2012;345:e6512
  1. Shanthi Kappagoda, fellow1,
  2. John P A Ioannidis, professor2
  1. 1Center for Primary Care and Outcomes Research and Division of Infectious Diseases and Geographic Medicine, Stanford University School of Medicine, Stanford, CA, USA
  2. 2Stanford Prevention Research Center, Department of Medicine and Department of Health Research and Policy, Stanford University School of Medicine, and Department of Statistics, Stanford University School of Humanities and Sciences, Stanford
  1. Correspondence to: J P A Ioannidis, Stanford Prevention Research Center, 1265 Welch Road, MSOB X306, Stanford, CA 94305-5411, USA jioannid{at}
  • Accepted 18 September 2012


Objective To assess the quantity and distribution of evidence from randomised controlled trials for the treatment of the major neglected tropical diseases and to identify gaps in the evidence with network analysis.

Design Systematic review and network analysis.

Data sources Cochrane Central Register of Controlled Trials and PubMed from inception to 31 August 2011.

Study selection Randomised controlled trials that examined treatment of 16 neglected tropical diseases or complications thereof published in English, French, Spanish, Portuguese, German, or Dutch.

Results We identified 971 eligible randomised trials. Leishmaniasis (184 trials, 23 039 participants) and geohelminth infections; 160 trials, 46 887 participants) were the most studied, while dracunculiasis (nine trials, 798 participants) and Buruli ulcer (five trials, 337 participants) were least studied. Relative to its global burden of disease, lymphatic filariasis had the fewest trials and participants. Only 11% of trials were industry funded. 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.

Conclusions There is considerable variation in the amount of evidence from randomised controlled trials for each of the 16 major neglected tropical diseases. Even in diseases with substantial evidence, such as leishmaniasis and geohelminth infections, some recommended treatments have limited supporting data and lack head to head comparisons.


  • Contributors: Both authors conceived the study, analysed the data, interpreted the results, drafted the manuscript, and approved the final version. SK extracted the data with help from JPAI. JPAI is guarantor.

  • Funding: SK was supported in part by grant HS000028 from the Agency for Healthcare Research and Quality. The content is solely the responsibility of the authors and does not necessarily represent the official views of the Agency for Healthcare Research and Quality. The funding source had no role in the design or implementation of the study or the decision to publish.

  • Competing interests: Both authors have completed the ICMJE uniform disclosure form at (available on request from the corresponding author) and declare: no support from any organisation for the submitted work; no financial relationships with any organisations that might have an interest in the submitted work in the previous three years; no other relationships or activities that could appear to have influenced the submitted work.

  • Ethical approval: Not required.

  • Data sharing: Dataset of the primary raw data is available on request from the corresponding author.

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