What does number needed to treat measure?

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Multiple Choice

What does number needed to treat measure?

The main idea is to express, on average, how many patients must receive a treatment to prevent one adverse outcome within a specified time frame. This is done by taking the reciprocal of the absolute risk reduction (ARR), which is the difference between the event rate in those not treated and in those treated. For example, if 8% of people in the control group have the adverse event and 4% in the treatment group do, the ARR is 4 percentage points. The NNT would be 1 divided by 0.04, which equals 25. So, about 25 people would need to be treated to prevent one adverse event over that time period. NNT depends on the time horizon and the specific outcome being measured. A lower NNT means a more effective preventive effect. It’s not a measure of how many people are cured, nor is it about how long it takes for treatment to work. It also doesn’t account for harms or costs—that’s where the related concept, number needed to harm, or other risk–benefit considerations, come in.

The main idea is to express, on average, how many patients must receive a treatment to prevent one adverse outcome within a specified time frame. This is done by taking the reciprocal of the absolute risk reduction (ARR), which is the difference between the event rate in those not treated and in those treated.

For example, if 8% of people in the control group have the adverse event and 4% in the treatment group do, the ARR is 4 percentage points. The NNT would be 1 divided by 0.04, which equals 25. So, about 25 people would need to be treated to prevent one adverse event over that time period.

NNT depends on the time horizon and the specific outcome being measured. A lower NNT means a more effective preventive effect. It’s not a measure of how many people are cured, nor is it about how long it takes for treatment to work. It also doesn’t account for harms or costs—that’s where the related concept, number needed to harm, or other risk–benefit considerations, come in.

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