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Centre for Evidence-
Based Medicine

Example NNTs - Infectious Diseases

Condition or Disorder Intervention vs. Control Outcome Follow-up Duration Event Rates % NNT (95% CI)
CER EER
AIDS1; Patients with HIV-1 infection and CD4+ lymphocyte count ≤ 100/mL Ritonavir vs. placebo AIDS-defining illness or death Median 28.9 weeks 37.5 21.9 6 (5 to 10)/td>
AIDS1; as above Ritonavir vs. placebo Death from any cause Median 51 weeks 23 16 14 (9 to 43)
Herpetic gingivostomatitis2 Acyclovir vs. placebo Oral lesions 8 days 70 6.5 2 (1 to 2)
Eating difficulties 47 6.5 3 (2 to 5)
Drinking difficulties 30 3.2 4 (2 to 11)
HIV infected persons with previous antiretroviral treatment3 Indinavir, zidovudine + lamivudine vs. zidovudine + lamivudine Changes in HIV RNA levels and CD4+ cell counts. 24 weeks 0 90 2
Shigellosis in Bangladeshi children4 Vitamin A vs. no vitamin A Clinical cure by day 5 5 days 20 45 4 (2 to 18)
Bacteriological cure from day 3 39 38 Not significant
HIV infection; breast-fed infants5 Zidovudine vs. placebo HIV-1 infection in the live-born children of women in the study 6 months 27.5 18 11 (6 to 100)
Sexually transmitted diseases in minority women6 Behavioral intervention (3 weekly group sessions in which recognition of risk, commitment to change and acquisition of skills were discussed) vs. control group (received 15 minutes of standard individualized counseling by nurse clinicians according to guidelines from the US Centers for Disease Control and Prevention) Subsequent infection with Chlamydia trachomatis or Neisseria gonorrhoeae, assessed by testing endocervical samples with DNA probes 6 and 12 months 26.9 16.8 10 (6 to 32)
HIV-1-infected patients with tuberculosis7 Trimethoprim-sulfamethoxazole (co-trimoxazole) vs. placebo Death 10.5 months 22.6 13.3 11 (7 to 26)
≥ hospitalization 12.4 7.6 21 (11 to 172)
HIV-1-infection8 Efavirenz plus zidovudine and lamivudine vs. indinavir plus zidovudine and lamivudine Percentage of patients with suppression of plasma HIV-1 RNA to < 400 copies/mL 48 weeks 48 70 5 (4 to 10)
meningitis9 Dexamethasone vs placebo death 8 weeks 25 15 1 (5 to 73)

References

  1. Lancet 1998; 351:543-9
  2. BMJ 1997 Jun 21;314(7097):1800-3
  3. N Engl J Med 1997 Sep 11;337(11):734-9
  4. BMJ. 7 Feb 1998; 316: 422-6
  5. Lancet 1999 Mar 6;353(9155):786-92
  6. N Engl J Med. 14 Jan 1999; 340: 93-100
  7. Lancet. May 1, 1999; 353: 1469-75
  8. N Engl J Med. Dec16, 1999; 341:1865-73
  9. NEJM. 2002;347:1549-56