Numbers needed to treat and absolute risk reduction

Numbers needed to treat and absolute risk reduction

Numbers needed to treat (NNT) is a measure that indicates how many patients would require an intervention to reduce the expected number of outcomes by one

Numbers needed to treat (NNT) is a measure that indicates how many patients would require an intervention to reduce the expected number of outcomes by one.

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Importance: 49

.

It is calculated by 1/(Absolute risk reduction)

NNT = 1 / Absolute Risk Reduction

You've never been tested on this concept

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Importance: 49

and is rounded to the next highest whole number

Experimental event rate (EER) = (Number who had particular outcome with the intervention) / (Total number who had the intervention)

Control event rate (CER) = (Number who had a particular outcome with the control/ (Total number who had the control)

Absolute risk reduction = CER-EER or EER-CER?

The absolute risk reduction (ARR) may be calculated by finding the absolute difference between the control event rate (CER) and the experimental event rate (EER). You will often find both versions of the above listed in different sources. In some ways in doesn't matter which you use as you will end up with the same answer but from a technical point of view:

• if the outcome of the study is undesirable then ARR = CER - EER
• if the outcome of the study is desirable then ARR* = EER - CER

*this may be more accurately termed absolute benefit increase, rather than absolute risk reduction

+PassMedicine Notes

Numbers needed to treat (NNT) is a measure that indicates how many patients would require an intervention to reduce the expected number of outcomes by one.

It is calculated by 1/(Absolute risk reduction) and is rounded to the next highest whole number

Experimental event rate (EER) = (Number who had particular outcome with the intervention) / (Total number who had the intervention)

Control event rate (CER) = (Number who had a particular outcome with the control/ (Total number who had the control)

Absolute risk reduction = CER-EER or EER-CER?

The absolute risk reduction (ARR) may be calculated by finding the absolute difference between the control event rate (CER) and the experimental event rate (EER). You will often find both versions of the above listed in different sources. In some ways in doesn't matter which you use as you will end up with the same answer but from a technical point of view:

• if the outcome of the study is undesirable then ARR = CER - EER
• if the outcome of the study is desirable then ARR* = EER - CER

*this may be more accurately termed absolute benefit increase, rather than absolute risk reduction