DESIGN: Cost-effectiveness analysis using a decision model based on previously published data. Outcome measures included costs and quality-adjusted life expectancy.

SETTING: Physician’s office.

PATIENTS/PARTICIPANTS: Hypothetically healthy, working adults < 65 years of age presenting with cough and fever during the influenza season.

INTERVENTIONS: Rapid testing or clinical diagnosis followed by treatment with amantadine, rimantadine, oseltamivir, or zanamivir compared with no antiviral therapy.

RESULTS: Base-case analysis: not giving antiviral therapy is the most expensive and least effective strategy, costing 471 per patient, mostly owing to time lost from work. Amantadine treatment increases life expectancy by 0.0014 quality-adjusted life years (QALYs) while saving471 per patient, mostly owing to time lost from work. Amantadine treatment increases life expectancy by 0.0014 quality-adjusted life years (QALYs) while saving 108 per patient relative to no antiviral therapy. Zanamivir is slightly more effective than amantadine, adding 0.0002 QALYs at an incremental cost of 31, or31, or 133,000 per QALY saved. All other strategies, including testing strategies, are both less effective and more expensive.

SENSITIVITY ANALYSIS: The model is sensitive to the probability of influenza infection, proportion of influenza caused by type B, the relative efficacy of the various drugs, and the value of a workday. At a clinical probability of influenza infection >20%, antiviral therapy is favored. As the proportion of influenza B increases, zanamivir is favored over amantadine. Testing is rarely indicated. Ignoring the costs of lost workdays, amantadine treatment costs $1,200/QALY saved.

CONCLUSIONS: Antiviral therapy with either amantadine or zanamivir is cost-effective for healthy, young patients with influenza-like illness during the influenza season, depending on the prevalence of influenza B.