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Centre for Evidence-
Based Medicine

Example NNTs - Urology

Condition or Disorder Intervention vs. Control Outcome Follow-up Duration Event Rates % NNT (95% CI)
Benign prostatic hyperplasia1 Finasteride vs. placebo Surgery for BPH 4 years 10.1 4.6 18 (13 to 27)
Acute urine retention 6.6 2.8 27 (19 to 43)
Urinary incontinence in women2 Bladder training or pelvic muscle exercises with biofeedback assisted instruction vs. combined bladder training plus pelvic muscle exercises Frequency of self reported incontinence 3 months 13 31 5 (3 to 23)
Perceived symptom improvement 30 52 4 (3 to 20)


  1. N Engl J Med. 26 Feb 1998; 338: 557-63
  2. Am J Obstet Gynecol. Oct 1998; 179: 999-1007