CDC again cautions against using rapid flu tests for H1N1 detection

CDC said findings from a recent H1N1 outbreak in the United States reaffirmed its recommendation against using rapid influenza diagnostics testing to ID the virus. It said, however, that RIDTs, which typically yield results in thirty minutes, can still be used to detect seasonal flu and suggested they may have value in certain settings, especially in hospitals that cannot afford real-time RT-PCR tests.

The analysis, which relied on a single undisclosed RIDT, said they “detected less than half the cases confirmed by rRT-PCR” and that “[t]he low sensitivity and low negative predictive value of the test during these outbreaks highlight the limitations of using this test alone to establish diagnosis and aid clinical management” of H1N1.

“These results affirm current recommendations not to use negative RIDT results to rule out pandemic H1N1 or to make infection control decisions,” CDC said in a statement, dated 25 September but released late yesterday afternoon.

The analysis was based on an H1N1 outbreak in a pair of schools in Connecticut this spring. It “affirm[s] recent CDC recommendations against using negative RIDT results for management of patients with possible 2009 pandemic influenza A (H1N1) infection,” the agency concluded.

Still, CDC said RIDTs “can be an important tool for patient care,” including making decisions about “isolating or cohorting patients in health-care settings and recommending or restricting patient movements in outpatient settings.”

RIDTs “might be especially important for hospitals limited by the expense of rRT-PCR and in identifying influenza during outbreaks in defined patient groups, such as those in schools or nursing homes,” CDC said.

The agency cautioned, however, that “if used for management of patients with possible pandemic H1N1 virus infection, false-negative [RIDT] test reports might result in inappropriate exposure of susceptible persons to infected patients.