by revere, cross-posted from Effect Measure

We’ve gotten the question here fairly frequently: If antivirals (Tamiflu, Relenza) for swine flu work best when given early but shouldn’t be given to people who aren’t really that sick, how do you balance waiting for them to get sick and have the drugs not work well with giving it when you don’t need to? There is no absolutely right answer to this difficult question. Early in the pandemic antivirals were being given prophylactically to stop spread, then they were being given only when a diagnosis of swine flu was confirmed. Then only to the sickest patients. We’re all on a learning curve. The latest recommendations from CDC try to walk the narrow line between over use and under use, taking into account that missing early treatment could endanger the lives of some patients who go on to serious illness. So the trick is to initiate early treatment for those at highest risk, even if some, or any, test results aren’t available or aren’t positive. For those patients, “empiric antiviral treatment” is indicated. Empiric treatment means use the drugs and ask questions later. From CDC’s Health Alert Network for health departments and clinicians:

The 2009 pandemic H1N1 influenza virus continues to be the dominant influenza virus in circulation in the U.S. The benefit of antiviral treatment is greatest when it is initiated as early as possible in the clinical course. Several recent reports have indicated two problems related to antiviral treatment: (1) some patients with suspected influenza who are at higher risk of developing severe complications, including hospitalized patients, were not treated at all with antiviral medications because of a negative rapid influenza diagnostic test result and (2) initiation of treatment was delayed for some patients with suspected influenza who are at higher risk of developing severe complications, including hospitalized patients, because clinicians were waiting for results of real-time reverse transcriptase-polymerase chain reaction (rRT-PCR) assay. (CDC Health Alert Network)

Who are the people at higher risk? Let’s start with the opposite. Who are the people who have or might have flu that CDC doesn’t think need immediate initiation of antiviral therapy? Most flu cases:

Most healthy persons (i.e., those without a condition which puts them at higher risk for complications) who develop an illness consistent with uncomplicated influenza do not need to be treated with antiviral medications and will recover without complications. However, clinical judgment should be the ultimate guide in making antiviral treatment decisions for ill persons who are not at higher risk for complications from influenza.

The main point about this. Treat the patient, not the lab tests. If you are otherwise healthy and have flu-like symptoms but don’t feel that bad, you don’t need antivirals. But whenever you feel really sick or have trouble breathing or have symptoms in your chest, regardless of how healthy you were before, you should see someone and probably get antivirals. If you didn’t feel so bad but now are getting worse, that is an indication, too. Age is not a factor, young or old. If you aren’t offered antivirals you should probably ask for them.

What are the categories of people who, when they get flu-like symptoms — fever or respiratory symptoms in the chest or sore throat or cough without other obvious cause — should be treated pre-emptively with antivirals? If you are sick enough to be hospitalized for suspect influenza, you should be started immediately on antivirals (Tamiflu or Relenza). If you not not sick enough for the hospital, here is the rest of CDC’s list of those for whom early empirical (independent of test results) antiviral treatment should be considered:

  • Children younger than 2 years old  
  • Adults 65 years and older  
  • Pregnant women  
  • Persons with the following conditions: 
  • Chronic pulmonary (including asthma), cardiovascular (except hypertension), renal, hepatic, hematological (including sickle cell disease), or metabolic disorders (including diabetes mellitus);  
  • Disorders that can compromise respiratory function or the handling of respiratory secretions or that can increase the risk for aspiration (e.g., cognitive dysfunction, spinal cord injuries, seizure disorders, or other neuromuscular disorders)  
  • Immunosuppression, including that caused by medications or by HIV;  
  • Persons younger than 19 years of age who are receiving long-term aspirin therapy, because of an increased risk for Reye syndrome. 

These are not automatic or easy decisions to make, either for health care providers or for patients. It would be wrong not to admit there are substantial uncertainties. The advice CDC is giving here seems the most rational and reasonable given what we know at this time. It is even possible it could save your life.

There’s a self-assessment tool at www.flu.gov and advice for parents and pregnant women that might be useful.

Here are some CDC links on the topic:

Updated Interim Recommendations for the Use of Antiviral Medications in the Treatment and Prevention of Influenza for the 2009-2010 Season: http://www.cdc.gov/H1N1flu/recommendations.htmInterim

Recommendations for Clinical Use of Influenza Diagnostic Tests During the 2009-10 Influenza Season: http://www.cdc.gov/h1n1flu/guidance/diagnostic_tests.htm

Questions & Answers:
Antiviral Drugs, 2009-2010 Flu Season: http://www.cdc.gov/h1n1flu/antiviral.htm

Influenza Diagnostic Testing: http://www.cdc.gov/h1n1flu/diagnostic_testing_clinicians_qa.htm

Updated Interim Recommendations for Obstetric Health Care Providers Related to Use of Antiviral Medications in the Treatment and Prevention of Influenza for the 2009-2010 Season: http://www.cdc.gov/H1N1flu/pregnancy/antiviral_messages.htm

Antiviral Drugs: Summary of Side Effects: http://www.cdc.gov/flu/protect/antiviral/sideeffects.htm