Skip to content

What is a “number needed to treat?”

July 24, 2008

Number needed to treat is a statistic calculated by epidemiologists (I am an epidemiologist by training) to determine how effective something is.

I was going to put the derivation and the formula here, but I decided that linking to Wikipedia was easier.

The real power of number needed to treat is in how easy it is to understand.  Let’s say that you do a study with Drug A and do all the statistics and find out that the number needed to treat is 3.  That means that to avoid getting Disease X, you have to give Drug A to 3 people.  Let’s say you do another study with Drug B and find out the number needed to treat is 100 (meaning you have to treat 100 people for the drug to work in 1 of them).  Which drug is more effective?

Well, if I want one person to get better, I have to give Drug A to 3 people or Drug B to 100 people.

To put it another way, if I gave Drug A to 100 people, 33 would get better.  If I gave Drug B to 100 people, only 1 would get better.

Man, maybe number needed to treat isn’t that easy to understand…

Advertisements
No comments yet

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: