Reviews and Perspectives with Hobart Lee: NNT
Hobart Lee, MD, and Heidi James, MD
Hoby joins Heidi to discuss the number needed to treat (NNT). This simple statistic is important for primary care docs to understand, to be able to explain to patients, and to know the rough numbers for some of the common interventions we prescribe to patients
- NNT helps us explain that all patients are helped by an intervention. Some benefit but most do not.
- How to calculate NNT:
- 1/absolute risk reduction (ARR)
- NNT is dependent on the baseline control rate. When the baseline event rate (ie, what happens in natural life with no treatment or intervention) is HIGH, then the NNT will be low. This can be particularly tricky if you are calculating NNT in a small trial where random expected variability can make the baseline control rate high.
- Number needed to harm (NNH):
- NNH is the “evil twin” of NNT. It is commonly used to describe events like side effects or adverse outcomes from an intervention like a new drug.
- Common NNTs:
- To prevent death at 5 years of treatment: NNT = 125
- To prevent stroke at 5 years: NNT = 67
- To prevent nonfatal myocardial infarction: NNT = 100
- Steroids for “sore throat,” with symptom improvement in 24-48 hours
- Statins to prevent heart disease
- Nonfatal heart attack: NNT = 217
- Nonfatal stroke: NNT = 313
- NNH of statins
- Myalgia = 21
- New-onset diabetes = 204
- NNT in prostate-specific antigen (PSA)-based prostate cancer screening (number needed to screen):
- For men 55-69 years, you need to screen 770 men to prevent 1 prostate cancer–related death.
- Recommended resources
PEARL: NNT and NNH are useful concepts to review with your patients when discussing therapeutics and screening.
Recommendation: Prostate Cancer: Screening https://www.uspreventiveservicestaskforce.org/uspstf/recommendation/prostate-cancer-screening
EMA 2019 May: Time To Talk A Little Nerdy: NNT and NNH
EMA 2018 June: Rick’s Rants: The Number-Needed-To-Treat
Ian L. - September 2, 2022 4:30 PM
With regards to hypertension it depends on level of hypertension and age and other co-morbidities.
Another site the NNT records tables by age 50 and 65 for a Systolic of 170 and the NNT for death overall is 125 although true there are harms bit NNH though 10 was for medication side effects .
In 'the NNT " for a 65 yesr old male systolic 170
NNTto prevent stroke over 5years is 88 and MI 101.
20 million USA males over 65 with a SYSTOLIC BP above 170 is alot -200,000 strokes prevented over 5 years .