School of Medicine researchers have demonstrated
the validity of a rapid laboratory test capable of determining whether
a patient has SARS (Severe Acute Respiratory Syndrome).
Frederick Nolte, professor of pathology, said the polymerase chain
reaction (PCR) test in his Emory Hospital molecular diagnostic laboratory
took about four hours to confirm the presence of the SARS virus
fragment in a sample provided by a laboratory in Germany.
The German laboratory, the Bernhard Nocht Institute for Tropical
Medicine, announced last month in a New England Journal of Medicine
paper that it had identified and sequenced a novel coronavirus that
appears to be the cause of SARS.
Nolte tested a fragment of the coronavirus’ RNA consisting
of about 300 base pairs in the BNI-1 region that had been isolated
by the German lab. He said synthesis of the chemical probes and
primers used to identify and amplify that specific sequence of genetic
material was the most time-consuming part of the test at Emory.
In PCR, minuscule traces of viruses or other genetic material can
be duplicated and amplified chemically.
The technique is capable of detecting the presence of about 100
copies of the virus per milliliter in a patient sample, which would
equate to a very low level of infection, Nolte said.
The test, which takes about four hours to run once the sample is
prepared, cannot be done in a doctor’s office but would have
to be sent to a relatively sophisticated hospital or clinical laboratory.
It can be applied to sputum, mucus or blood samples.
Many researchers around the world are working to find positive diagnostic
tests since SARS remains an elusive diagnosis based primarily on
patients’ symptoms and history, including overseas travel
to Asia. The CDC has announced that only a fraction of suspected
cases of SARS in the United States are regarded as “probable.”
The SARS epidemic has been concentrated in Asia and Toronto, Canada.