This cost-effectiveness analysis demonstrates that community-based older adults benefit from antiviral therapy through an improvement in quality-adjusted life expectancy, if they begin treatment within 48 hours of influenza-like illness. The benefit comes at a cost. Under most circumstances, antiviral therapy is reasonably cost-effective and within the range of other widely accepted interventions for older adults, such as cholesterol reduction in patients with diabetes (41) or screening mammography (42). The optimal strategy, however, depends on the patient's vaccination status, the probability that he or she has influenza, and the risk for hospitalization (Figure 4). Empirical treatment with oseltamivir is most cost-effective when the probability of influenza or hospitalization is high. Rapid diagnostic testing followed by oseltamivir treatment, although less effective than empirical treatment, is cost-effective for low-risk patients and vaccinated patients, especially during the peri-influenza season, when influenza is unlikely and empirical treatment is very expensive. Withholding antiviral therapy is appropriate only for low-risk, vaccinated patients during the peri-influenza season.
Figure 1. Decision node ( ), chance events ( ), and terminal nodes ( ) are shown. The actual model contains four antiviral therapy branches, one for each antiviral drug. ED = emergency department.
Decision model treating influenza-like illness in older adults.squarecirclesdiamondsGrahic Jump Location
Figure 2. The testing strategies begin by testing all patients; those whose test results are positive are treated with the drug shown. The two curves represent vaccinated and unvaccinated patients. The lines represent the efficiency frontiers. The slope of the line between two strategies represents the marginal cost-effectiveness of one in relation to the other. Strategies below the line are dominated (that is, more expensive and less effective than one of the strategies on the frontier). QALY = quality-adjusted life-year.
Incremental cost-effectiveness of testing and treatment strategies for a 75-year-old patient with influenza-like illness.Grahic Jump Location
Figure 3. The curves represent the marginal cost-effectiveness of each strategy compared with the next best strategy for unvaccinated ( ) and vaccinated ( ) patients. The graphs are divided into three zones representing different probabilities of influenza: peri-influenza season, peak season, and regional epidemic. QALY = quality-adjusted life-year.
The cost-effectiveness of antiviral therapy or testing as a function of the probability of influenza.topbottomGrahic Jump Location
Figure 4. The strategy providing the most quality-adjusted life-years at a marginal cost-effectiveness at or below $50 000 per quality-adjusted life-year saved. The percentages at the top of the figure are probabilities of influenza infection based on timing of presentation. Influenza season varies from year to year. Peak season is generally from December through February in the northern hemisphere; peri-influenza season months include October, November, March, and April; and “regional epidemic” denotes an area where influenza has recently been reported to be widespread. * Cost-saving in unvaccinated patients; † Cost-saving in all patients.
Optimal influenza therapy based on risk, season, and vaccination status.Grahic Jump Location
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