Number Needed to Treat (NNT) is calculated as the reciprocal of:

• A Relative Risk Reduction (RRR)
• B Odds Ratio minus 1
• C Attributable Risk Percent in exposed
• D Absolute Risk Reduction (ARR) ✓

Explanation

NNT = 1/ARR, where ARR = Control Event Rate (CER) minus Experimental Event Rate (EER). NNT represents the number of patients who need to be treated to prevent one additional adverse outcome. The Relative Risk Reduction (RRR = ARR/CER) does not directly give NNT; using RRR to calculate NNT requires knowing baseline risk. NNT is a clinically intuitive measure of therapeutic efficacy and is more meaningful than RRR when assessing treatment value across different baseline risk groups.

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.