More evidence needed

Consider the need for further fair comparisons.

There is always some uncertainty about the effects of health actions. If that uncertainty affects decisions that are important to people, the uncertainty should be reduced by further fair comparisons whenever possible.


Many decisions about health actions must be made despite their effects being uncertain. The uncertainty may be due to a lack of comparisons, or due to low certainty evidence from studies. Fair comparisons can reduce the uncertainty about health actions. Individuals should consider participating in fair comparisons when they are uncertain about which health action to choose because of uncertainty about the effects of the available options. Participating in a fair comparison has several advantages:

  • It can be a good choice when there is important uncertainty about effects, and you are not sure what to do.
  • It can be an opportunity for learning.
  • Participants in fair comparisons may be more closely monitored, and treatment guidelines may be followed more carefully. Because of this, participants in fair comparisons may fare better than people outside of fair comparisons.
  • The results of fair comparisons can help to generate reliable information on which to base future decisions. Many people welcome the opportunity to participate for altruistic reasons or to make a difference by contributing to science.
  • Trial participation can be a win-win situation – one in which participants can both help others and benefit (or at least not be harmed) personally.

A common reason for not participating in fair comparisons (randomized trials) is a strong preference for (or against) one of the health actions being compared.

In addition to personal considerations about the pros and cons of participating in a randomized trial, people should only participate in trials if:

  • The trial protocol has been registered and made publicly available.
  • The protocol refers to a systematic review showing that the trial is justified.
  • You receive written assurance that the full study results will be published and sent to all participants who indicate that they wish to receive them.

To increase the value of research and reduce waste, new fair comparisons should always address the needs of users of research (patients, health professionals, and policymakers) and be informed by systematic reviews of existing research.


A study interviewed people about their motivation to participate in a trial of surgery compared to medical (drug) management of heartburn caused by gastroesophageal reflux (the flow of stomach acid and sometimes food back up into the tube that connects the mouth to the stomach (the oesophagus)). It found that people invited to participate viewed:

  • recruitment appointments as an opportunity for learning,
  • participation as potentially offering access to surgery, and
  • participation as offering careful monitoring.

Participants said that wanting to assist others made them more likely to participate in the trial, but considerations of the personal implications of participating also influenced their decisions about participation. For the people who agreed to be randomized, trial participation seemed to be a win-win situation – one in which they could both help others and benefit (or at least not be harmed) personally.

Remember: Consider advocating for and participating in fair comparisons of health actions when there are important uncertainties about the effects of the health actions.

Educational resources for this concept
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