UPDATE November 2025
The 2025 update to the NICE Heart Failure guideline now includes new recommendations for this (previously borderline) category of heart failure.
In summary, it recommends considering an ACE inhibitor, beta-blocker, MRA and SGLT2 inhibitor in this situation.
However, the evidence base is much more limited than for heart failure with reduced ejection fraction.
We’re working on it and will have further information up here in early December 2025.
People who have an adverse event
People whose adverse event is prevented by treatment
People who were never going to have an adverse event anyway
Graphics and NNTs are rounded to the nearest integer
These three statistical terms offer three different ways of looking at the results of trial data.
Absolute Risk Reduction
This tells you how many people out of 100 who take a treatment have an adverse event prevented.
MoreThe value of the ARR changes with the baseline risk of the person (or population) taking the treatment. The higher the starting risk, the greater the absolute chance of benefit.
You need to think about over what time the trial data show this benefit, as it is usually assumed that more absolute risk reduction is gained over time.
Your patient might be taking the treatment for much longer than the length of a clinical trial (or, if life expectancy is limited, perhaps for less time).
Number Needed to Treat
This tells you how many people need to take the treatment in order for one person to avoid an adverse event.
The lower the number, the more effective the treatment.
MoreThe value of the NNT changes with the baseline risk of the person (or population) taking the treatment. The higher the starting risk, the smaller the NNT.
You need to think about over what time the trial data show benefit, as it is usually assumed that more benefit is gained over time and therefore the NNT will drop over time.
Your patient might be taking the treatment for much longer than the length of a clinical trial (or, if life expectancy is limited, perhaps for less time).
Relative Risk Reduction
This tells you the proportion of adverse events that are avoided if the entire population at risk is treated.
MoreThe value of the RRR is usually constant in people (or populations) at varying degrees of risk.
It is also usually assumed to stay constant over time.
This can be helpful, especially when thinking about population outcomes, but can be misleading for an individual person:
For example, a RRR of 25% in someone with a baseline risk of 40% would give them an ARR of 10% and an NNT of 10.
A RRR of 25% in someone with a baseline risk of 4% would give them an ARR or 1% and an NNT of 100.
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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.