If evidence is rated as LOW quality, this does not mean it is totally unreliable!
For practical purposes, the spectrum of evidence quality going down from HIGH to MODERATE to LOW tells us that there is increasing uncertainty about the size of the treatment effect (i.e., there could be more or less benefit). LOW doesn’t usually mean that the treatment is unlikely to work or that we should not work with this evidence.
VERY LOW QUALITY evidence might well mean there is genuine uncertainty about whether a treatment works. Where this is the case, we give further information to help clarify.
How is evidence quality appraised on GP Evidence?
We use the GRADE system of evidence quality rating1,2, which is used by NICE and Cochrane among others.
Where NICE or Cochrane have performed a GRADE rating, this is reported here on this website. Where a GRADE rating has not been done, we perform our own assessment according to the GRADE structure.
GRADE provides a structured way to assess evidence quality. Though it is designed to be objective and reproducible, there is a degree of subjectivity involved in making judgements.
How does it work?
In a nutshell:
Randomised Controlled Trials and Meta-analyses are regarded as HIGH quality evidence, but can be downgraded for a variety of reasons.
Observational Research is initially rated as LOW quality, but can be upgraded for a variety of reasons.
Factors which can lead to a downgrading of evidence quality are:
Factors which can lead up an upgrading of observational research are:
References and links
1)GRADE working group website. Contains explanations, tutorials, links to literature.
This website is designed for use by General Practitioners and other healthcare professionals. The content is not exhaustive and assumes a standard level of GP professional knowledge. The information here is intended to support clinical judgement and shared decision making alongside clinical guidelines and standard practice.
If you are a patient/member of the public, do feel free to look around, but please don’t make any changes to your treatments based on information here. If you find something which seems relevant to you, you could show this website to your healthcare professional to help a discussion.