New molecular virus tests changing treatment practices

New molecular techniques are facilitating the rapid detection of viruses - including the 2009 influenza A H1N1 – but what pediatricians do with the information gained from these diagnostics depends upon the type of virus and the type of symptoms that virus is causing.

“Just because a test will detect a virus doesn’t mean it causes illness,” said Janet Englund, MD, of the University of Washington and Fred Hutchinson Cancer Research Center. Englund spoke on new molecular diagnostic testing at the Pediatric Academic Societies Annual Meeting held in Baltimore this week. She said these diagnostics are very sensitive, and they “will really change how we take care of patients.”

Englund said accurate viral diagnostic tests are important for infection control and infectious disease surveillance, and that is “evident if you listened to CNN today,” she said, noting the CDC’s call this week for accurate testing and reporting of the swine flu cases. She added that these tests are also important for patient cohorting and guiding treatment choices.

She cited data out of Alaska that showed results of molecular diagnostics of viruses there. In a study presented at the Infectious Diseases Society of America, Singleton et al showed that there was a shift from year to year on how much human metapneumovirus and respiratory syncytial virus predominated in the community there.

Another study presented by Fairchok et al noted that although rhinoviruses are by far the most common viruses circulating among day care attendees, RSV caused more serious illness. Englund cited data by Noyola et al that demonstrated that those patients who were diagnosed with influenza by EIA were less likely to receive antibiotics and more likely to be prescribed antivirals.

Many of these studies have shown that many viruses, influenza, RSV, parainflunza, bocavirus, coronaviruses and others cocirculate.

She said the newer diagnostics, like Luminex, offer the advantages of speed, reliability, reproducability, and the ability to type many viruses simultaneously. However, extreme sensitivity of these tests may lead to false positives and may also detect latent viruses even if they are not making the patient sick, which may lead to overtreatment.

EIA kits are useful for detecting every type of flu, including the now circulating swine flu. She said PCR can also be used for detection of influenza, but researchers must know what their target is to detect all influenza. As an example, she said swine flus are located on the pb1 or H genes of flu.

Englund said that careful studies are going to be needed to help researchers categorize prevalence of various respiratory illnesses in certain populations and to use that information to guide treatment decisions. –by Colleen Zacharyczuk

Englund J. #3415. Presented at: Pediatric Academic Societies Annual Meeting. Baltimore, MD; May 2-5, 2009.