Rapid diagnostic use common during influenza A (H1N1) pandemic despite unreliability

After the first cases of H1N1 appeared in April 2009, many diagnostic manufacturers submitted devices to the FDA for approval under Emergency Use Authorization to quickly detect the spread of illness. As of January 2010, 14 devices have been approved for H1N1 detection using this path, but most are not for point-of-care use, according to information presented at the 2010 Annual Conference on Antimicrobial Resistance in Bethesda, Md.

Although molecular tests such as real-time reverse transcription polymerase chain reaction were available through public health labs at state health departments during the pandemic, clinicians had limited access to these tests for routine clinical management and experienced difficulties obtaining test results from public health labs quickly enough to facilitate treatment options. Therefore, many turned to their old workhorses — the rapid influenza diagnostic tests.

Although rapid tests were useful in expediting H1N1 diagnoses, clinicians faced problems with test sensitivity during the height of the pandemic, according to CDC researcher Daniel B. Jernigan, MD, MPH.

Jernigan cited data that indicated that eight pregnant women were not administered antivirals on a timely basis, six of whom had negative test results. Although it is unclear whether those test results led to a lack of prescription, Jernigan said that earlier detection would have made choosing the right treatment options easier for clinicians.

Package inserts accompanying tests also claimed higher sensitivity than actually demonstrated, Jernigan noted. For example, the package insert for QuickVue Influenza Test (Quidel) states that the test has a sensitivity of 77% to 94% for influenza A, but data from studies indicated that sensitivity was actually much lower, ranging from 65% to 70%. Additionally, the BinaxNow Influenza A Test (Inverness Medical) had sensitivity only around 40%.

“Clinicians should take steps to improve the rapid test results by optimizing specimen collection and appropriate test use following package inserts,” Jernigan said. “Patients with suspect flu and negative rapid tests should be treated empirically based on underlying conditions, severity of illness, increase in complications and improvement in the rapid test performance through new test developments.”

During questions after the presentation, Jernigan and Frederick G. Hayden, MD, from the University of Virginia Health Systems, said that new treatment guidelines are expected from WHO later this week. – by Melissa Foster

For more information:

Jernigan DB. Clinical and public health implications of rapid diagnostic testing for influenza. Presented at: 2010 Annual Conference on Antimicrobial Resistance; Feb. 1-3, 2010; Bethesda, Md.