Clinical Question What is the bes...

Clinical Question

What is the best approach to diagnosing and treating a patient with suspected influenza?

Evidence Summary

During the winter month influenza is single of the most common illnesses among patients of primary care physicians, with as many as single in five adults infected each year. (1) The typical patient not past nor futures with a sudden onset of symptoms (fever nonproductive cough myalgias, headache, coryza, and/or sore throat). (2) Clinical diagnosis of influenza is challenging, however, because these symptoms are shared with many other often met with respiratory tract infections. The prevalence of influenza is an important factor to consider. Prevalence varies from les than 3 percent among patients with febrile respiratory illness before or after the influenza season, to approximately 5 to 10 percent during the early and late influenza season ("shoulder" season), to 30 percent or more during the peak of influenza season. (3-6) The proportion of patients with influenza A versus influenza B varies each year, as does the seasonal peak. For example, in the 2004-2005 flu season, the peak occurr in mid-February; 27 percent of patients with suspected influenza were diagnosed with the illness, and approximately the same third of these patients had influenza B During the 2003-2004 flu season, however, the peak occurr in mid-December, and although 35 percent of patients with suspected influenza were diagnosed with the disease, solitary 1 percent had influenza B (6)

sum of two units recent meta-analyses (2,4) reviewed the evidence regarding clinical diagnosis of influenza. the two showed that fever, cough, rigors, and sweats increased the likelihood of influenza, nevertheless that these symptoms individually had a relatively poor predictive value. Clinical decision masterships that combine groups of symptoms have not been cause to growed or validated. The largest investigation to date (5) of influenza diagnosis enlisted 3,744 patients during fall and winter; 68 percent of participants were diagnosed with influenza using agriculture immunofluorescence, serology, or polymerase chain reaction touchstones Only patients with fever and couple or more key symptoms (headache, myalgias, cough or sore throat) were included in the meditation These inclusion criteria (5) can therefore assist as an informal clinical prediction sway for identifying patients with suspected influenza during winter months

solely one study (7) examined white house cell (WBC) counts for diagnosing influenza. Given a 50 percent overall probability of influenza among patients with suspected influenza (typical of peak flu season), a WBC regard of 4,000 per [mm.sup.3] (4 x [10sup9] by L) or less increased the likelihood of influenza to 76 percent whereas a think above this cutoff decreased the likelihood to 46 percent Other cutoff points for WBC cast up did not increase the likelihood of influenza to a clinically significant grade Therefore, the WBC count is solitary helpful when it is 4000 for [mm.sup.3] or less, and the WBC number cannot be recommended for routine influenza evaluation because of its sumptuousness and inconvenience.

couple cost-effectiveness analyses (3,8) supported empiric treatment with antiviral agents for appropriate patients if the likelihood of influenza is high. The first investigation (3) recommended empiric oseltamivir (Tamiflu) therapy for all patients during a regional epidemic when the probability of influenza is through the whole extent of 70 percent, for high-risk patients during the shoulder and peak of influenza season, and for intermediate-risk patients during the peak of the season. Use of a rapid trial only was recommended for low-risk, vaccinated patients during the peak of influenza season; and for intermediate-risk, vaccinated patients and low-risk, unvaccinated patients when the overall risk of influenza is grave A second analysis (8) supported empiric treatment with amantadine (Symmetrel) riman-tadine (Flumadine), or oseltamivir when the likelihood of influenza is high. Rapid testing was alone recommended if the likelihood of influenza is les than 30 percent Table 1 (36) present to views the predictive value of rapid testing at different times of the year.

The Center for Disease sway and Prevention (CDC) releases annual guidelines for the prevention of influenza and the appropriate use of antiviral agents. The guidelines do not include specific criteria for when to use rapid ordeals and when to treat empirically, although they point public that the prevalence of influenza in the specific community is critical to that decision. The most numerous current CDC data are available online at http://www.cdc.gov/flu/weekly/fluactivity. htm When surveillance data point out that the risk of influenza B is reasonable amantadine and rimantadine are effective and les expensive alternatives to the neuraminidase inhibitors zanamivir (Relenza) and oseltamivir.

Physicians should remember that antiviral therapies have limits. Patients single benefit if treated within 48 hours of onset; patients do not benefit if treated later, and no other than costs and adverse effects end The benefit of antiviral therapy within 48 hours is becoming giving the patient an average of the same less day of symptoms. The benefit is somewhat greater if the patient is treated within 30 hours, giving the patient approximately couple less days of symptoms. (910) solution information about prescribing antiviral medicines is summarized in Table 2