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Annals of Emergency Medicine – Influenza Testing

Jessica Mason, MD and Larissa May, MD
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Nurses Edition Commentary

Lisa Chavez, RN and Kathy Garvin, RN

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EM:RAP 2018 04 April Written Summary 535 KB - PDF

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Tim V. -

The Cochrane Review says neuraminidase inhibitors don’t work, why do you recommend treatment?

Larissa M., MD -

Thanks for bringing this up-indeed we realize the controversy around antivirals and thus specifically avoid it in the Annals Commentary! The 2014 Cochrane Review does in fact conclude limited benefit from the use of NI, while more recent systematic reviews (Doll et al, J Antimicrobial Chemotherapy, 2017) suggest there may be a reduced incidence of mortality. There are unfortunately few high quality RCTs particularly in high risk populations such as young children. I do not recommend either testing or treatment in healthy adults. However, in certain settings reducing transmission is important (nursing homes, immune suppressed patients). For high risk patients with underlying cardiopulmonary disease, young children, those being hospitalized the benefit of treatment likely outweighs the risk. Main side effects are vomiting (and possible neuropsych effects in the elderly). I do employ shared decision making with patients. CDC and professional society guidelines still recommend treatment for high risk patients. We have nothing else to offer them other than supportive treatment. I personally however am much more concerned about the overuse of antibiotics for many conditions including patients with viral respiratory infection, prophylaxis for wounds, etc. where the evidence is even less compelling. The side effects of antibiotics (C. difficile, anaphylaxis) are much greater than what is reported for antivirals and yet as an EM community there is a gap in addressing their use in folks who are not high risk. There remains a lot of controversy about antivirals, and we need higher quality trials but in the meantime I think of treating high risk patients in a similar way to making a decision about an antibiotic in a high risk patient with an abscess vs simply discharging them after I and D.

Tim V. -

Thanks for your insightful thoughts.

Ian L., Dr -

The rapid PCR tests are available .
The Biofire Film Array Respiratory Panel 2 claims to be able to test for 22 pathogens in 45 minutes : influenza A and B RSV Bordetella Pertussis Mycoplasma Pneumonia and the RP2 respiratory syndrome coronovirus .
Leber et al Jclinical Microbiology 2018 March 28
The Cobas Liat test tests for PCR influenza A and B and still pyrogens claim within 20 minutes .
Young S et al Jclinical virology 2017 .
But expensive : Test Equipment said to cost $A25,000 each test with labor $100 .
For high risk patients to begin .

Larissa M., MD -

Thank you for your comment. Unfortunately cost effectiveness studies are often lacking. The BioFire test is a multiplex panel that is typically $100 per test after capital investment. It gives a lot more information beyond the presence of influenza or RSV including pertussis and a whole host of other pathogens (e.g. rhinovirus, adenovirus, metapneumovirus) that may fail to pass the ED physician's "so what" test. The Liat tests are molecular point of care tests. The unit may retail much higher however institutions have been able to get contracts at 12.5 k per machine. Each test costs about $25 to run. They are > 95% sensitive and specific. While the patients to test may remain debatable, the molecular tests represent a paradigm shift in diagnosis. The rapid antigen tests provide very little if any clinical utility and their use on a grand scale (EDs, urgent cares, primary care) drives up cost with little benefit.

Ian L., Dr -

The early diagnosis within hours of Bordetella Pertussis and Mycoplama Pneumonia Influenza A and B and RSVwill be of great benefit particularly in Pregnant patients Patients immunocomprised elderly and very young .
There needs to be validation in Emergency Urgent care and Primary Care that is obligation
As for reduction of antibiotic usage in general practice and outpatients a viral diagnosis in a cough persisting @1 3 7 14 day with the pressure to prescribe ZPak accentuating at each visit ought help .

Mark M., MD -

The "high risk" patients you suggest in your comments are fairly narrow (eg hospitalized very old, very young, immuno-compromised...) but the "high risk" the CDC recommends includes a large segment of the ED population (morbid obesity, diabetes,older than 65, "cardiopulmonary disease" , liver disease...) both inpatient and outpatient. The opportunity for unnecessary treatment outpatient, not to mention the cost of over $100 for a precription and the extra time spent in the ED waiting for test results can not be justified with any information we currently have for outpatient Tami-flu.
Before a test is promoted, we must discuss the time in ED, cost to patient, and value of treatment for the outpatient. The fact that some providers want to overtreat with an antibiotic and/or an antiviral does not diminish the argument that unnecessary and expensive medications should not be prescribed if they are proven unhelpful regardless of what the ED tests show.

Larissa M., MD -

I completely agree with you that implementation of diagnostic testing needs to be considered-simply bringing in new tools and expecting their use and implementation will immediately impact patient care is naive at best. I'm hopeful diagnostic companies are becoming more interested in cost effectiveness studies. And agree indiscriminate use in the outpatient setting should not be promoted

Tiffany K. -

I was in Northern New Zealand at the height of a meningococcal meningitis epidemic during flu season and we were urged to abandon influenza testing as a "rule out" meningitis for the fever/headache patients specifically because many people harbor meningococcus in their normal nasopharyngeal flora and influenza infection can "open up" the usual mucosal barrier, essentially promoting CNS access for the resident bacteria and increasing the rate of meningitis. I would urge caution in your recommendation to use a positive influenza test to rule out meningitis, even with our low meningitis incidence. I consider positive influenza to be a risk factor for meningitis.

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