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.