New technology IDs infections

Vera Misenheimer, 94, is all smiles and even sings her visitors a little tune inside her room at Medical Col­lege of Georgia Hospital and Clinics. She is obviously feeling better in her second day there but is ready to go home.


“The sooner the better,” she said.

Her daughter, Delane Mc­Alis­ter, said her mother had been very ill.

“We had thought it was pneumonia,” McAlister said. “It turned out it was a little pneumonia and a whole lot of flu.”

Thanks to new technology at the hospital, doctors know it was the influenza A H3 subtype, the dominant strain of this year’s flu season, that caused her illness and might lead to an earlier discharge.

Knowing it is a virus and not bacteria, and knowing which viruses are occurring when, is the point of having the FilmArray Respiratory Pathogen PCR technology, doctors said.

PCR stands for polymerase chain reaction, a way of taking small amounts of genetic material from a patient sample and amplifying it many times. In this case, it is run against known reference sequences for 15 common viruses and three bacteria known to cause respiratory infections.

Many of these infections show the same symptoms, said Dr. Dennis L, Murray, the chief of pediatric infectious disease at Georgia Re­gents University.

For instance, respiratory syncytial virus and human metapneumovirus are often the culprits when there is wheezing, Murray said.

“But parainfluenza (virus) can cause wheezing, influenza can cause wheezing,” he said.

Knowing what the cause is will help better determine the treatment, Murray said. If it is bacterial, that could help determine the antibiotic treatment. But if it is viral, that is another story, he said.

“Most of these viruses, with the exception of influenza, at this time most of them we don’t have a specific antiviral drug for,” Murray said. “What we can do about it is we can prevent you … from getting antibiotics.”

Overuse of antibiotics is fueling the rise of antibiotic-resistant bacteria, and doctors and organizations like the Centers for Disease Control and Prevention are working to prevent prescribing them inappropriately.

Knowing a virus is to blame could allow a patient to leave for home a little sooner, Murray said.

The PCR test also helps provide a better diagnosis than tests that look for a specific virus antigen, such as many rapid flu tests.

“Those are notorious for having poor sensitivity and specificity,” said Dr. Christine Litwin, the director of clinical microbiology and immunology at GRU, who helped bring PCR testing to the hospital.

Antigen tests either can’t detect the virus or lack the ability to correctly identify it. That is particularly true of rapid flu tests, which have been shown to be anywhere between 27 percent to 61 percent accurate in correctly identifying strains, according to a recent CDC study.

That study looked at the 11 rapid flu tests approved by the Food and Drug Administration. One failed to routinely detect influenza A samples even at high concentrations. Four picked up most influenza B viruses but only one got at least 50 percent of the influenza A viruses at lower virus concentrations such as those that might be found in a clinical setting, according to the CDC study.

Beyond flu, the PCR test can show what other important viruses and bacteria are circulating at different times of the year, which reveals a “fascinating” pattern, Murray said. That is particularly true this year, Litwin said.

“It is interesting this year that the influenza A really came very, very early,” she said, in November and December and all but disappearing this month. Respira­tory syncytial virus, an important cause of respiratory illness in very young children, appears to do a kind of cycle with influenza, Murray said.

“Interestingly enough, if flu starts at the same time, RSV tends to go way down,” he said. “And then it comes back again once flu has left town. They are very competitive.”

Because of the cost of running the PCR test, it is probably not appropriate for use in a clinic or doctor’s office, Murray said.

“Who knows, five to 10 years from now, PCR may be so commonplace and so easily done it can be done in a clinic, in a doctor’s office, for a relatively low cost,” he said. “That’s the future of these products.”

Litwin, who worked with the lab that helped to develop the technology before coming to GRU, thinks that might be the case.

“I am hopeful for that, that it will be more useful around the United States eventually,” she said.



Sun, 10/22/2017 - 00:18

Faces of Survival: Karen McMichael