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EBM library: Systematic reviews to support humanitarian medicine

The EBM library signposts some essential reading for the practice of Evidence-Based Medicine. In this part of the library, we highlight the role of systematic reviews in humanitarian medicine.

Kamal Mahtani

Systematic reviews have made significant contributions to the pool of best available evidence in healthcare. In a previous post, I explored the importance of systematic reviews to healthcare policymakers and the challenges that come with trying to increase their uptake. To mark Humanitarian Evidence week, I discuss an example of how a systematic review has influenced humanitarian medicine.

Paper: Clasen TF et al. 2015. Interventions to improve water quality for preventing diarrhoea. The Cochrane Library.

According to the World Health Organization (WHO), diarrhoeal disease is the second leading cause of death in low-income countries, with estimates of 57 deaths per 100,000 population. In contrast, mortality from diarrhoeal disease is not listed in the top 10 causes of death in high-income countries. One main factor for this disparity is the poor water sanitation found in low-income countries, which leads to higher rates of microbiological contamination.

Effective interventions to improve water sanitation, particularly at the point of use, are therefore likely to prevent a considerable number of deaths. In their Cochrane review, Thomas Classen and colleagues evaluated interventions to improve water quality for preventing diarrhoea. They classified these interventions into four categories:

  • Physical removal of pathogens (for example, filtration, adsorption, or sedimentation).
  • Chemical treatment to kill or deactivate pathogens (most commonly with chlorine).
  • Disinfection by heat (for example, boiling or pasteurisation) or ultraviolet (UV) radiation (for example, solar disinfection or artificial UV lamps).
  • A combination of these approaches (for example, filtration or flocculation combined with disinfection).

They identified 55 relevant studies, sampled from mostly lower-middle or low-income countries including 84,023 participants.

Six of the included studies (four cluster RCTs and two quasi RCTs) evaluated solar water disinfection (SODIS) interventions. This type of disinfection originated in the 1980s and involves the use of UV radiation from sunlight. Bottles made from polyethene terephthalate (PET –  a sort of recyclable plastic) are first cleaned with soap. The bottles are then filled with water, sealed, and placed in direct sun exposure, e.g. on top of a low roof, for at least 6 hours. A newspaper is positioned underneath and, if after 6 hours the letters of the headline are readable, the water can be used.

From the four cluster RCTs evaluated in the systematic review, there was moderate quality evidence that the use of SODIS treatments reduced the risk of diarrhoea by about a third. There are several other advantages to SODIS: simplicity of use and acceptability; low cost if using recycled plastic bottles, minimal change in taste of the water, and a low risk of recontamination if water is served and stored in small narrow-necked bottles.

Disadvantages of SODIS also need to be considered: the need to pretreat water of high turbidity, the limited volume of water that can be treated all at once, and the need for extensive stocks of PET bottles.  Nevertheless, the impact of the evidence for the use of SODIS has been considerable. The US Centers for Disease Control and Prevention estimate that over 2 million people in 28 developing countries use SODIS for daily drinking water treatment. 

Evidence from systematic reviews has the potential for far-reaching impact. As highlighted above, this extends into humanitarian medicine. If you are interested in this area, the Evidence Aid website contains a collection of assessed published systematic reviews identified as being of relevance to natural disasters, humanitarian crises, or major healthcare emergencies.

Kamal R Mahtani is a GP and Deputy Director of the Centre for Evidence-Based Medicine, Nuffield Department of Primary Care Health Sciences, University of Oxford. He is also the Director of The Evidence-based Healthcare MSc in Systematic Reviews  

You can follow him on Twitter @krmahtani

Disclaimer: The views expressed in this commentary represent the views of the author and not necessarily those of his host institution, the NHS, the NIHR, or the Department of Health.

Acknowledgements: Jeffrey Aronson & Carl Heneghan for helpful discussions. Pictures from Wikipedia (By SODIS Eawag – Own work, CC BY 3.0,

Competing interests: Kamal Mahtani receives funding from the NIHR School for Primary Care Research Evidence Synthesis Working Group and is Director of a MSc in Systematic reviews.


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