Blog | Tuesday, August 21, 2012

QD: News Every Day--rapid tests not always accurate for swine-origin influenza

Rapid diagnostic tests are not always accurate for swine-origin influenza, the Centers for Disease Control and Prevention reported last week.

The CDC recently tested seven commercially available rapid influenza diagnostic tests (RIDTs) to evaluate their accuracy in detecting influenza A (H3N2) variant virus. Only four of the seven tests were able to detect all seven influenza A (H3N2) variant strains. One test detected five of seven, one test detected three of seven, and one test detected only one of seven. The results were published online by MMWR.

An accompanying editorial note emphasized that a negative RIDT result should not be considered conclusive when testing for influenza A (H3N2) variant virus. "Results from RIDTs, both positive and negative, always should be interpreted in the broader context of the circulating influenza strains present in the area, level of clinical suspicion, severity of illness, and risk for complications in a patient with suspected infection," the note said. "Clinicians should minimize the occurrence of false RIDT results by strictly following the manufacturer's instructions, collecting specimens soon after onset of influenza-like illness (ideally within the first 72 hours), and confirming RIDT results by sending a specimen to a public health laboratory."

Further guidance from the CDC on this topic is available online.