Quick DNA Tests Crack Medical Mysteries Otherwise Missed
Researchers are developing a radical way to diagnose infectious diseases. Instead of guessing what a patient might have, and ordering one test after another, this new technology starts with no assumptions.
The technology starts with a sample of blood or spinal fluid from an infected person and searches through all the DNA in it, looking for sequences that came from a virus, a bacterium, a fungus or even a parasite.
Scientists at the University of California, San Francisco are reporting this week their first results from the technique, which relies on a technology calledNext Generation Sequencing.
One of their early patients is Andrea Struve, a 21-year-old San Franciscan who returned from 40 days in the Australian Outback last year with a nasty set of symptoms.
"I was in classes, sweating profusely with a fever and joint pain, and it just wasn’t fun, so that’s when I went to the doctor," she says.
Her doctor made a bunch of educated guesses about the underlying cause, but all the tests came back negative. So physicians enrolled Struve in a study at UC San Francisco to try out a different approach.
"As opposed to the way we normally diagnose infectious disease — meaning we target a single infectious agent at a time — this test works by detecting all the DNA present in clinical samples," says Dr. Charles Chiu, who is running the study.
Chiu extracted DNA from Struve’s blood and ran it through a superfast sequencing machine. He compared the DNA he found with a huge library of DNA sequences from all sorts of infectious agents. It turns out that she was infected with a virus related to chicken pox — one that normally causes a roseola rash in young children.
Photo: Doctors used a rapid DNA test to identify a Wisconsin teen’s unusual infection with Leptospira bacteria (yellow), which are common in the tropics. (CDC/Rob Weyant)