theNNT Rating System

Our Therapy (NNT) Approach

For every therapy we review, we provide a color-coded summary for you to use (borrowed from the traditional stoplight). As we state in our philosophy, we care about benefits and harms that matter to patients, not researchers. Patients care about death and illness, not a laboratory value or CT scan finding. We use this focus on "patient-important outcomes" to guide our recommendations.

The Green Rating

Green. Go.

Therapies rated green are the best you can get – there is clear evidence of patient-important benefits, and these benefits clearly outweigh any associated harms. For example: Steroids for Asthma Attack: if you give steroids to 8 patients with asthma attack in the emergency department, you prevent one from having to be admitted to the hospital. There are definitely side effects to steroids – high blood sugar, hyperactivity – but these, to us, seem minor in comparison.

See All Therapy (NNT) Reviews Rated Green

The Yellow Rating

For us at theNNT, therapies rated yellow require more study. We don't think the data is conclusive or substantial enough to be able to give a clear rating yet. It's the yellow therapies that we think would benefit from large, randomized controlled trials (when possible and appropriate) to give us a better sense of if we're helping patients when these medicines are given or wether we're harming them.

See All Therapy (NNT) Reviews Rated Yellow

The Red Rating

Red suggests that benefits and harms may be equal or equivocal; while there may be some benefits, in our opinion the benefits don't outweigh the harms. One extreme example: if a medicine were to save 2% of people's lives, but cause strokes in 10% of people, it's hard to say that this medicine clearly is overall helpful.

See All Therapy (NNT) Reviews Rated Red

The Black Rating

Black is our "worst" or "lowest" rating. Therapies rated black have very clear associated harms to patients without any recognizable benefit. One example: liberal transfusions for patients with anemia. Patients who received more blood transfusions did not do any better than patients with fewer (more restrictive) blood transfusions, but were much more likely to develop pulmonary edema, which can be life-threatening and require intensive care to manage.

See All Therapy (NNT) Reviews Rated Black

Our Diagnosis (LR) Approach

For every diagnostic evaluation we review, we also provide a color-coded summary of how helpful each sign/symptom/test is for that particular disease process; the darker the blue, the more important or helpful the criteria. Because of the way that likelihood ratios affect disease risk and odds, we've also made criteria that are unlikely to help change a patient's risk not usable with our dynamic risk calculators. You'll notice these values are in grey, and can't be clicked. These values are positive likelihood ratios less than 2 or negative likelihood ratios of greater than 0.5.


As you're probably aware if you're reading this, there are downsides to trying to categorize everything into neat little boxes – some therapies may not fit well into our schema. While we acknowledge it's not perfect, we still feel it's a useful way to get a quick assessment of the utility of a therapy. Some of the ratings are certainly open to interpretation, so again, we've done our best to pick a rating that we can all support and agree upon, but if you feel strongly that our assessment is wrong, please feel free to contact us. We'd love to hear from you! This is also why we've chosen to provide a summary of our interpretation of the data along with links to the primary sources, so you can read for yourself if you disagree with our assessment.