A nice opportunity for me to show the usefulness of this:
It may surprise folk to know that many modern-day medical interventions [including 'ahem' exercise) are far from miracles (see examples in pic). But NNT of 8 & 25 is right up there w the best.
/1
It may surprise folk to know that many modern-day medical interventions [including 'ahem' exercise) are far from miracles (see examples in pic). But NNT of 8 & 25 is right up there w the best.
/1
Borrowing* figures from:
(*herein lies one of the problems with press-released data raised by others:
)
We can use @d_spiegel tool to explore how we can communicate the #RECOVERYtrial findings
understandinguncertainty.org/node/233
/2
(*herein lies one of the problems with press-released data raised by others:
)
We can use @d_spiegel tool to explore how we can communicate the #RECOVERYtrial findings
understandinguncertainty.org/node/233
/2
Let's look at the group of patients who required 02 but not ventilation:
We first determine the proportion (risk) of people that died in the group NOT receiving dexamethasone (dexa) =
2750/550 = 0.20 (20%). Note that 80% of these people survived with no dexa anyway.
/3
We first determine the proportion (risk) of people that died in the group NOT receiving dexamethasone (dexa) =
2750/550 = 0.20 (20%). Note that 80% of these people survived with no dexa anyway.
/3
Next we determine risk of death (in time frame of the study period) in the group treated w dexa =
1375/220 = 0.16 (16%). So 84% of people in the dexa group survive, an increase of 4% compared w the no dexa group. That's one way to communicate the findings
There are others
/4
1375/220 = 0.16 (16%). So 84% of people in the dexa group survive, an increase of 4% compared w the no dexa group. That's one way to communicate the findings
There are others
/4
Here's a cates plot that shows what happens when we give dexa to 100 people (this is known as natural frequencies & is helpful to visualise the impact on people as opposed to %).
4 people (yellow) on dexa receive the benefit.
/5
4 people (yellow) on dexa receive the benefit.
/5
However, you will see that 80 people (green) will not have died anyway, and 16 people (red) will still unfortunately die (in the study time period) even when taking dexa.
The risk tool allows you to visually display the findings in different ways - here's a column chart.
/6
The risk tool allows you to visually display the findings in different ways - here's a column chart.
/6
The tool also allows you to express the findings using text only, and to frame the findings negatively ('experiencing the event') or positively ('being free from the event) - I really like this as it changes the whole perspective
Here is an example of positive framing
Here is an example of positive framing
And here's the same findings framed negatively:
/8
/8
Here's what the visual displays look like when framed negatively:
/9
/9
So far we've been looking at the risk in a population of 100. But folk most likely want to know "what's my chance/risk?"
The tool also allows for this - from both a positive perspective ("avoiding):
10/
The tool also allows for this - from both a positive perspective ("avoiding):
10/
And a negative perspective ("experiencing"):
/11
/11
Many have talked about the number needed to treat (also called "NNT") which is the number of people who need to take dexa for one ADDITIONAL person to be sparred an earlier death
Math = 1 (or 100 if using %) divided by the absolute risk difference = 1/0.04 (100/4) = 25
/12
Math = 1 (or 100 if using %) divided by the absolute risk difference = 1/0.04 (100/4) = 25
/12
The tool also provides this as text:
/13
/13
We've been talking only about the absolute risk (ie. the difference in risk in one group versus the other). But the data that have been released are relative risks (ie. the risk on one group relative to the risk in the other)
The tool lets you display relative risks too.
/14
The tool lets you display relative risks too.
/14
Here is the relative risk framed positively as a column chart:
/15
/15
And framed negatively:
/16
/16
And positively and negatively framed using text only:
/17
/17
To sum up:
- The #RECOVERYtrial provides an NNT that is right up there w the best of interventions across medicine
- When considering the actual impact, remember the people here = COVID-19 requiring 02 but non-ventilated
- 80% of these DID NOT DIE in the study time period
/18
- The #RECOVERYtrial provides an NNT that is right up there w the best of interventions across medicine
- When considering the actual impact, remember the people here = COVID-19 requiring 02 but non-ventilated
- 80% of these DID NOT DIE in the study time period
/18
- 20% of them did die in the study period
- When these people are given dexa, 4 out of 100 (4%) of them do not die
- You can frame these findings in many different ways & this may make a difference in how the findings are perceived
/19
- When these people are given dexa, 4 out of 100 (4%) of them do not die
- You can frame these findings in many different ways & this may make a difference in how the findings are perceived
/19
- Whilst "Your chance" is what everyone wants to know, we CAN'T ACTUALLY KNOW if you will be:
a. one of the 80 people who will survive anyway
b. one of the 4 who will be saved early death w dexa Rx
c. one of the 16 who will die regardless of dexa Rx
End
a. one of the 80 people who will survive anyway
b. one of the 4 who will be saved early death w dexa Rx
c. one of the 16 who will die regardless of dexa Rx
End
Soz. Broke the thread. Continues here:
A correction to this tweet:
Where I say "4 out 100 (4%) did not die", this should be "an extra 4 in 100 (4%) do not die compared with those not given dexa"
16 in 100 still die with dexa.
80 in 100 will survive without dexa.
Where I say "4 out 100 (4%) did not die", this should be "an extra 4 in 100 (4%) do not die compared with those not given dexa"
16 in 100 still die with dexa.
80 in 100 will survive without dexa.
Further notes:
It seems obvious that all would choose to have a chance of being one of the 4 that dexa keeps alive longer.
But we also need consider any potential harm(s) associated with the treatment. Like the benefit(s), we cannot know of the harm(s) will happen to you.
It seems obvious that all would choose to have a chance of being one of the 4 that dexa keeps alive longer.
But we also need consider any potential harm(s) associated with the treatment. Like the benefit(s), we cannot know of the harm(s) will happen to you.
Here the potential harm(s) probably don’t outweigh the benefit so most would choose treatment.
Question is who chooses in this context? The patient or the health professionals caring for them?
And how much of the above:
a) is discussed?
b) matters if it’s discussed or not?
Question is who chooses in this context? The patient or the health professionals caring for them?
And how much of the above:
a) is discussed?
b) matters if it’s discussed or not?
