Originally created 11/06/01

A quicker way to test for anthrax unveiled



WASHINGTON -- Scientists have developed a DNA test that may identify anthrax spores in a letter, building or person in just 30 minutes - and this week will begin studying whether a "smart bomb" type of medical test can diagnose inhaled anthrax well before symptoms appear.

The first test, developed by the Mayo Clinic, is intended to prove that anthrax and not some other bacteria is present in the environment - not to diagnose a sick person.

But researchers at the Walter Reed Army Medical Center are hopeful the second test, called LeuTech, might help people survive inhaled anthrax by identifying such patients before they become seriously ill. To prove that, researchers on Tuesday will begin enrolling 500 people recently exposed to anthrax in the study.

Both tests are highly experimental. Roche Diagnostics, which manufactures Mayo's DNA test, said it plans to begin shipping test kits to certain laboratories later this week, although the Food and Drug Administration has not yet approved the tests' use. Roche must meet federal rules for labs to use the tests experimentally, said FDA spokeswoman Sharon Snider, but is expected to do so.

As for LeuTech, it can diagnose certain infections well enough that the FDA next year is expected to approve its use in diagnosing atypical appendicitis, said manufacturer Palatin Technologies Inc. The Walter Reed experiment marks its first attempted use against anthrax.

Two major problems have dogged anthrax testing since the bioterror attack began: how to quickly prove whether people were exposed to anthrax or to related but harmless germs, and how to diagnose the potentially deadly inhaled form of anthrax quickly enough to save those patients.

The Mayo DNA test promises to help solve the first problem.

Today, workers use quick "field tests" as a first step in detecting anthrax contamination. But those tests aren't very accurate, and testing to prove that anthrax and not a related bacterium is present takes from six hours to two days.

With the new DNA test, "we're talking about less than an hour instead of days," said Mayo microbiologist Franklin Cockerill. "This should deter some of the anxiety."

The technology uses four DNA probes to identify the presence of anthrax genetic material, instead of the single DNA probe commonly used, he said. Studies using laboratory samples of human blood suggest it is very accurate, he said.

But Dr. Bradley Perkins of the Centers for Disease Control and Prevention cautioned that the new DNA test must be carefully compared to CDC's own genetic anthrax tests to ensure it is as accurate.

Under the FDA's expected rules, labs are to use the Mayo test kits to check just for the presence of anthrax spores - such as from suspicious powder or a nasal swab of someone suspected of breathing anthrax - not illness, Roche officials said.

Roche plans to ship 100 test kits to each of the 25 labs by the end of this week.

LeuTech, in contrast, is being studied as a way to catch actual illness earlier than today's X-rays or even sophisticated CT scans can.

LeuTech is a radiolabeled monoclonal antibody, a molecular bloodhound that seeks out infection-fighting blood cells called neutrophils and causes them to glow when viewed under a special gamma ray camera.

Neutrophils cluster at the site of any bacterial infection. The anthrax theory: well before anthrax causes the lungs' lymph nodes to enlarge enough to be spotted any other way, LeuTech should light up neutrophils battling those germs, explained Walter Reed's Dr. Robert Bridwell, who approached Palatin about the study.

Because so many people exposed to anthrax already are taking protective antibiotics, it may be hard to prove if LeuTech works - someone has to get sick for that to happen, acknowledged Palatin president Carl Spana.