The number needed to treat (NNT) is BEST defined as:
- A 1 divided by the absolute risk reduction ✓
- B 1 divided by the relative risk reduction
- C The reciprocal of the number needed to harm
- D The odds ratio minus 1 divided by the event rate
Correct answer: A. 1 divided by the absolute risk reduction
Explanation
NNT = 1 / Absolute Risk Reduction (ARR), where ARR = risk in control group minus risk in treatment group. It represents the number of patients who need to be treated to prevent one additional outcome event. Using relative risk reduction in the denominator gives an inflated (falsely optimistic) NNT. NNT and NNH are related measures but are not reciprocals of each other.
Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.