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Centre for Evidence-
Based Medicine

Example NNTs - Dermatology

Condition or Disorder Intervention vs. Control Outcome Follow-up Duration Event Rates % NNT (95% CI)
Intravenous skin antisepsis1 0.5% chlorohexidine gluconate (CHG) vs. 70% isopropyl alcohol swab followed by povidone-iodine swab (control) Local catheter related infection 72 hours 12.5 1.2 9 (5 to 23)
CHG vs. povidone-iodine swab followed by 70% isopropyl alcohol swab (control) 9.9 1.2 12 (6 to 48)


  1. Can J Infect Con. 2000; Spring: 9-14