Newer and highly accurate molecular tests that deliver results in 15-60 minutes should be used to diagnosis influenza instead of currently employed rapid-influenza diagnostic tests (RIDTs), according to updated guidelines released by the Infectious Diseases Society of America (IDSA).

The guidelines published in Clinical Infectious Diseases pointed out that RIDTs produce quick results but that accuracy can be in issue, explaining that the tests can be falsely negative in at least 30% of outpatients with influenza.

Doctor looking at computer. Source: Getty

Authors of the new guidelines endorsed influenza testing overall, noting that physicians are more likely to treat patients with antiviral medications if they have a definitive diagnosis. That reduces the likelihood of prescribing antibiotics inappropriately, especially in outpatients, they add.

Once influenza is confirmed, patients not at high-risk of complications should receive antiviral treatment if their illness began two days or less before presentations, according to the guideline panel.

Clinicians are urged to start antiviral treatment as soon as possible for adults and children at high risk of complications, including those with chronic medical conditions or are immunocompromised, children younger than 2 or adults 65 or older and pregnant women and those within two weeks post-partum.

The previous guidelines were published just before the 2009 H1N1 influenza pandemic, the fourth pandemic in the past 100 years. The authors describe how last year’s flu season, although not a pandemic, caused about 49 million illnesses in the United States, including 960,000 hospitalizations and 79,000 deaths.

"We are always concerned about preparing for the next pandemic, but we also are focused on preventing and controlling seasonal influenza," said Timothy M. Uyeki, MD, MPH, MPP, co-chair of the guidelines committee and chief medical officer of the Influenza Division of the National Center for Immunization and Respiratory Diseases at the CDC.. "While pandemics aren't predictable, we know that every year we're going to have seasonal influenza and we need to improve how we prevent and control it through influenza vaccination, better diagnosis and early antiviral treatment of patients."

The guidance emphasizes that early treatment with antivirals reduces the duration of symptoms and risk of some complications, such as bronchitis, otitis media, and pneumonia, and hospitalization, and might decrease mortality among high-risk populations.

At the same time, the authors stressed that annual vaccination is the best method for preventing or mitigating the impact of influenza, although they add, “in certain situations, chemoprophylaxis with antiviral medications can be used for preexposure or postexposure prevention and can help control outbreaks in certain populations.”

In terms of testing, guideline authors write, “Use of available diagnostic modalities and proper interpretation of results can accurately identify patients presenting with influenza. Timely diagnosis may decrease unnecessary laboratory testing for other etiologies and use of antibiotics, improve the effectiveness of infection prevention and control measures, and increase appropriate use of antiviral medications.”

In addition to diagnostic testing, the update document adds new information on use of antivirals, and considerations of when to use antibiotics and when to test for antiviral resistance. It also offers evidence on harm associated with routine use of corticosteroids.