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Centre for Evidence-
Based Medicine

Example NNTs - Primary Care

Condition or Disorder Intervention vs. Control Outcome Follow-up Duration Event Rates % NNT (95% CI)
CER EER
Chronic fatigue syndrome1; Patients reporting fatigue (medically unexplained, lasting ≥6 months) Cognitive behaviour therapy vs. orthodox medical care Improved function 6-7 months 26.7 73.3 3 (2 to 5)
Head lice2; Patients of any infected with live lice Pediculicides (e.g., permethrin) vs. placebo Freedom from viable lice or eggs 14 days 5.9 97 2 (1 to 2)
Nosocomial pneumonia3 Semirecumbent body position (45° from the horizontal) vs. supine body position Clinically suspected nosocomial pneumonia 72 hours 34 8 4 (3 to 11)
Microbiologically confirmed nosocomial pneumonia (by bronchoalveolar lavage or protected specimen-brush cultures 23 5 6 (4 to 29)
Influenza4 Oral oseltamivir once daily vs. placebo Laboratory-confirmed influenza-like illness 6 weeks 4.8 1.2 27 (17 to 59)
Oral oseltamivir twice daily vs. placebo 4.8 1.3 29 (17 to 69)
Ventilator-associated5 Invasive management strategy (fiberoptic bronchoscopy to obtain protected specimen-brush samples or bronchoalveolar lavage samples to guide treatment vs. Clinical management strategy (control-clinical evaluation, examination of Gram-stained endotracheal aspirates and adherence to the American Thoracic Society guideline recommendations for choosing antiboitics) All-cause mortality 28 days 26 16 11 (6 to 56)
Dissolving earwax6 Docusate sodium vs. triethanolamine polypeptide (control) Complete visualisation of the tympanic membrane (with or without irrigation) 35 81 3 (2 to 6)
Sepsis7 Immune enhancing enteral feeding formula vs. control formula Mortality 32 19 8 (4 to 637)
Acquired bacteraemia 22 8 8 (4 to 28)
≥1 acquired nosocomial infection 20 6 8 (5 to 23)
Influenza8 Influenza vaccine vs. placebo Patients reports of fever plus cough or sore throat and associated physician visits and lost work days during influenza period during flu season of 1998-99 After flu season was finished 10.2 1.4 12 (7 to 27)

References

  1. Price JR, Couper J. Cognitive behaviour therapy for adults with chronic fatigue syndrome. Cochrane Review, 24 Aug 1998. In: The Cochrane Library. Oxford: Update Software.
  2. Interventions for treating headlice. Cochrane Review, 14 Jan 1999. In: The Cochrane Library. Oxford:Update Software.
  3. Lancet. Nov 27, 1999; 354: 1851-8
  4. N Engl J Med. Oct 28, 1999; 341:1336-43
  5. Ann Intern Med. Apr 18, 2000; 132: 621-30
  6. Ann Emerg Med. Sep 2000; 36: 228-32
  7. Crit Care Med. Mar 2000; 28: 643-8
  8. JAMA. Oct 4, 2000; 284: 1655-63