Number Needed to Treat - USMLE Forums
USMLE Forums Logo
USMLE Forums         Your Reliable USMLE Online Community     Members     Posts
USMLE Articles
Go Back   USMLE Forums > USMLE Step 1 Forum

USMLE Step 1 Forum USMLE Step 1 Discussion Forum: Let's talk about anything related to USMLE Step 1 exam

Thread Tools Search this Thread Display Modes
Old 12-21-2009
USMLE Forums Scout
Steps History: CK+CS
Posts: 77
Threads: 4
Thanked 32 Times in 31 Posts
Reputation: 42
Stats Number Needed to Treat

Kaplan video said it's the reverse of incidence while UW said it's the reverse of absolute risk reduction!
Which one is correct?
Reply With Quote Quick reply to this message

Old 12-21-2009
DrSeddik's Avatar
USMLE Forums Veteran
Steps History: 1+CK+CS
Posts: 236
Threads: 57
Thanked 452 Times in 107 Posts
Reputation: 465

Number Needed to treat is the number of patients you needed to treat, so that one patient can get the benifit of the drug. That is, if on experiments 1% got a better result from the drug than placebo (ARR=1%), if you elimenate the effect of chance, you need to treat a 100 patients so that one would get the benifit (be the 1%). This is obtained from 100/1, inverted ARR.

Number Needed to Treat for harm has the same concept, but instead of ARR, it is absolute harm increase, which's the incidence difference of an adverse effect between placebo and the those who took the drug.

So at least UW is more accurate, but limited to number needed to treat to benifit (NNTB, or NNT), I don't know what incidence Kaplan means, but maybe it's either ARR or absolute harm increase..
Reply With Quote Quick reply to this message
The above post was thanked by:
Ahmed-USMLE (12-21-2009), kalpana (12-21-2009), Sabio (12-21-2009), Taiwan_Guy (05-16-2011)
Old 12-21-2009
USMLE Forums Master
Steps History: 1+CK+CS+3
Posts: 3,318
Threads: 170
Thanked 4,844 Times in 1,808 Posts
Reputation: 4897

Both of them are right
One divided by the incidence (reciprocal) will give you the number needed to reach out in order to prevent the occurrence of disease. For example if the incidence of influenza in certain population is 5 in 1000 per year then you need to vaccinate (1000/5 = 200) people in order to prevent one influenza case per year.
However, that's not the most common way NNT is used in medical journals. It's usually the reciprocal of ARR. Which basically means how many cases you have to treat in order for the new intervention/therapeutic measure/drug ...etc can prevent/improve one case in the population of the study. For example, if the incidence of DM retinopathy is 20% in people treated with OHA and 15% in people treated with glitazones then you have prevented 5% (which is your ARR) and so you need to treat 20 patients to achieve that difference.

Please note that NNT should always be a sound number. If your calculation ended up 5.9 then you have to round it up to 6 because you cannot treat 5.9 individuals
Reply With Quote Quick reply to this message
The above post was thanked by:
DrSeddik (12-21-2009), kalpana (12-21-2009), memory (12-22-2009), mmtj (05-11-2012), Taiwan_Guy (05-16-2011)



Quick Reply

Register Now

In order to be able to post messages on the USMLE Forums forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
User Name:
Please enter a password for your user account. Note that passwords are case-sensitive.
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:
Medical School
Choose "---" if you don't want to tell. AMG for US & Canadian medical schools. IMG for all other medical schools.
USMLE Steps History
What steps finished! Example: 1+CK+CS+3 = Passed Step 1, Step 2 CK, Step 2 CS, and Step 3.

Choose "---" if you don't want to tell.

Favorite USMLE Books
What USMLE books you really think are useful. Leave blank if you don't want to tell.
Where you live. Leave blank if you don't want to tell.


Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Similar Threads
Thread Thread Starter Forum Replies Last Post
Help Advice Needed! ayash USMLE Step 1 Forum 2 04-05-2010 09:58 PM
CK Advice Needed ac1994 USMLE Step 2 CK Forum 5 03-01-2010 07:37 PM
CK number of questions losalola USMLE Step 2 CK Forum 1 02-03-2010 05:47 AM
USMLE Step 1 number of Questions Haytha USMLE Step 1 Forum 2 10-23-2009 09:03 PM
spinal nerve number repon32 USMLE Step 1 Forum 2 09-15-2009 08:54 PM

RSS Feed
Find Us on Facebook
vBulletin Security provided by vBSecurity v2.2.2 (Pro) - vBulletin Mods & Addons Copyright © 2016 DragonByte Technologies Ltd.

USMLE® & other trade marks belong to their respective owners, read full disclaimer
USMLE Forums created under Creative Commons 3.0 License. (2009-2014)