False Negative Rapid Test Results Delay Therapy in Patients with Severe Flu Infections

New research from investigators at the Chang-Gung Memorial Hospital in Taoyuan, Taiwan, finds that about half of the influenza cases in patients who are admitted to the intensive care unit had received a false-negative rapid influenza antigen test (RIAT). False negative results could delay needed treatment in patients with severe infection.

The findings were presented at the 2018 ASM Microbe meeting held this year in Atlanta, Georgia.

Rapid influenza diagnostic tests (RIDTs) are immunoassays that are used to identify the presence of influenza in respiratory specimens in less than 15 minutes. However, according to the Centers for Disease Control and Prevention (CDC), although these tests are able to yield results in a clinically relevant time frame, they have limited sensitivity compared with reverse transcription-polymerase chain reaction (RT-PCR) or viral culture. False negative results have been known to be common with these tests, especially when flu activity is high.

For their study, investigators conducted a retrospective analysis from August 2009 to July 2017 of 307 patients with influenza who were admitted to Chang-Gung Memorial Hospital’s ICU. RIAT was performed on 259 of the 307 confirmed cases, and 126 (49%) tested negative for the virus. Furthermore, 45 (15%) of the 307 cases either tested negative on all upper respiratory tract samples or did not have those samples tested; diagnosis of the cases was made based on lower respiratory tract samples.

Authors of the study stress that about half of the cases assessed in the study came up with negative RIAT results and a negative test result could be misleading to health care providers, prompting them to dismiss influenza as a diagnosis.

“As physicians specialized in infectious disease, we advocate that testing of the LRT samples are crucial for diagnosis of severe influenza with critical illness,” Po-Yen Huang, MD, lead investigator of the study said in a recent statement.

The authors also noted that patients who tested negative via RIAT shared similar characteristics with the RIAT-positive cases; however, they actually required longer stays in the ICU (median 12 vs 9 days) and longer ventilator days (median 12 vs 6 days). Additionally, the investigators found antiviral treatment to be significantly delayed in the RIAT-negative patients (median 1 vs 0 days).

“Negative RIAT results delayed treatment with antiviral medication,” Dr Huang stressed. “Decision making for antiviral medication should be provided to all critically ill patients with severe respiratory infection.”