Benefit and Risk Flashcards
What is the equation for NNT (number needed to treat)?
100% divided by the difference of the sample group percentage that died/had an unwanted effect on placebos minus the group percentage that died/had an unwanted effect while taking a drug of interest
=1/ARR, RRR doesn’t help much
What is NNT?
N.N.T. tells us how many people must be treated for one person to derive benefit. An N.N.T. of one would mean every person treated improves and every person not treated fails to, which is how we tend to think most therapies work
In contrast, there is a complementary metric known as the number needed to harm, or N.N.H., which says that if that number of people are treated, one additional person will have a specific negative outcome.
What is an example of relatively low NNT?
As treatments go, an N.N.T. of 30 is pretty good. Very few are as low as 10, though some are. For instance, the use of steroids in people having asthma attacks to prevent admission to the hospital has an N.N.T. of eight.
NNT for use of antibiotics with ear infection
As another example, let’s consider antibiotics for ear infections in children. There are many reasons that parents and pediatricians might consider treatment. One commonly cited reason is that we want to prevent serious complication from untreated infections. Unfortunately, antibiotics don’t do that, and the N.N.T. is effectively infinite. Antibiotics also won’t reduce pain within 24 hours. Antibiotics have, however, been shown to reduce pain within two to seven days. Not all children will see that benefit, though. The N.N.T. is about 20 for that outcome.
Antibiotics can cause side effects, however, including vomiting, diarrhea or a bad rash. The N.N.H. for side effects in this population is 14.
This means that when a child is prescribed antibiotics for an ear infection, it’s more likely that he will develop vomiting, diarrhea or a rash than get a benefit. When patients are presented with treatment options in this manner, they are sometimes more likely to agree to watchful waiting to see if the ear infection resolves on its own. For most children with ear infections, observation with close follow-up is recommended by the American Academy of Pediatrics.
