Newer rapid influenza tests have an improved ability to rule out disease but are still better at ruling in influenza, and a change in management should be considered before testing, according to a clinical synopsis published in the Annals of Emergency Medicine.

A systematic review of 124 peer-reviewed studies of adult and pediatric patients with suspected influenza that compared the diagnostic accuracy of the newer rapid tests (digital immunoassay, rapid nucleic acid amplification test, and rapid influenza diagnostic test) against the reference standard (reverse transcriptase polymerase chain reaction) was conducted. Results indicated that digital immunoassays and rapid nucleic acid amplification tests provide higher sensitivities (ranging from 76.8% to 95.4%), and high specificities (>98%). The rapid nucleic acid amplification tests had an overall negative likelihood ratio less than 0.1, making them the only test that could usefully rule out influenza.

Performance of the commercial assays did vary widely, and investigators caution that “more than half of studies involving rapid influenza diagnostic tests and rapid nucleic acid amplification tests had selection bias or were at high risk of bias.” Further, they state that results should be interpreted with caution because of the risk for bias from industry sponsorship. “The majority of the digital immunoassay (68%) and rapid nucleic acid amplification test (62%) studies were sponsored by industry, and a sensitivity analysis found that industry sponsorship was associated with higher sensitivities.”

Current Centers for Disease Control and Prevention guidelines recommend influenza testing only if the results would change clinical management or if patients are being hospitalized. Physicians, therefore, should use the newer rapid tests within the context of each patient encounter and recommend testing “only if test results would change clinical management or if patients are being admitted to the hospital.”

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Pettit K, Welch JL. Update: can newer rapid influenza tests rule out disease? [published online February 13, 2018]. Ann Emerg Med. doi: 10.1016/j.annemergmed.2018.01.020