Sifting the evidence

What is evidence? 

Evidence is having proof or confirmation that something is true or that something works. Information obtained without proof or evidence is called hearsay or anecdotal evidence and is usually obtained by casual observation or passed around by word-of-mouth.

 

Why do we need evidence in healthcare?

In the healthcare setting, people are often faced with decisions and choices about different parts of their care – such as undergoing tests, procedures or surgeries and starting on medicine or other treatments.

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Frequently people have questions such as:

• What are the risks and benefits?

• What are the pros and cons?

• Will it work?  

• How well will it work?

• Is it safe?    

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When making decisions, it is important that choices are made on the basis of the most up-to-date, solid, reliable scientific proof or evidence. Without evidence, there is a chance of choosing an option that will not be the best for you or that may cause you harm.

 

Where does evidence come from?

Scientific evidence is usually obtained by performing clinical trials (also called fair tests), in which a treatment or medicine is compared to another treatment or medicine, or is compared to placebo (which is a fake version of the treatment, such as a sugar pill).

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• Clinical trials are made as fair as possible by reducing the effect of chance or bias.

• The results of clinical trials show whether a treatment works or doesn't work and whether it is safe or harmful.

 

What do I need to consider when judging evidence?

Understanding and interpreting the evidence can be quite complex. Your healthcare professional will be able to discuss the pros and cons of different options with you. 

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When sifting through evidence, remember that:

• different people respond differently to treatments

• not all people have the same risk or chance of experiencing a benefit or an adverse effect

• the evidence may not always be in line with your personal preference

• if a disease or condition is rare or unusual, there may be very little good quality evidence.​

 

How can I tell if the evidence is strong?

Sometimes there are hundreds of clinical studies, involving hundreds or even thousands of patients, that have similar results. In such cases, the evidence is described as strong.

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At other times, results from different studies may be conflicting or inconclusive – in this case, the evidence is described as weak and this makes decision making harder or more challenging. 

 

Learn more

The following links provide further information on evidence:

What is evidence? NHS, UK
Working out what's reliable evidence Ask for Evidence 
Making sense of health evidence – the informed consumer FutureLearn 
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