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Flowing Evidence into Cost Analysis: Powerful Ways with Number-needed-to-treat (NNT)
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Cost Analysis & NNT Example
This example serves several purposes.
- It illustrates the critical importance of including time period in NNT in order to better understand efficacy.
- It shows how you can use NNT in an effectiveness and cost analysis.
1. Read the fictional scenario below. This is typical of the kinds of issues faced by doctors, P & T committees, QI staff, etc., daily.
2. Think about your reaction.
3. Then look at the graphic to see how important NNT can be. Remember, NNT is always to be associated the length of the time of study. This example drives this home.
- Lifetime risk of hip fracture in women is 15% with significant mortality (20-30% of women die in the first year following hip fracture).
- HRT is now found to have many risks. Other fracture prevention drugs have risks. There is a new (fictional) drug on the market that has fewer risks and that many docs are starting to use on high and moderate risk women. The drug is getting a lot of press attention and has good evidence behind it.
- Many women in your organization are requesting information and treatment for prevention of fractures. Many are asking about this new drug.
- One year of treatment is cheaper than alendronate.
Should you treat these women with this new drug? How do you decide?
In our fictional scenario,
by switching from our current care to our new drug, we will have done
- Significantly reduced
quality of care. We will now prevent roughly 80 hip fractures compared
to roughly 138 prevented with current treatment in a course of 14.5
- Significantly increased
our expenses. We will now have spent $3.6MM less in prevention treatment,
but will have significant new expenses due to the increase in hip fractures.
This examples shows several
- You can do a simple, yet
powerful "back-of-the-envelope" analysis using a spreadsheet
- You need to look at prevalence
data in your population, consider what you are currently doing, assess
the evidence and then do sensitivity analyses to explore potential impacts
of practice change.
- Flowing evidence into
your cost analysis is highly important and revealing. In this instance
we see that even though a new drug may be less expense per year of treatment,
we are actually significantly reducing our quality of care AND increasing
our expenses by making a switch.
To compute a cost per
benefit, which you can then use for comparison purposes:
Quick Equation #1: NNT
x study period x dollars per time unit
OR #2: NNT x study period cost
- Many times people talk
about NNT without including the appropriate associated time period.
We see by this example, that it is this difference in time periods between
the old agent and the new that has made the significant difference.
At Cost Analysis & NNT
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