The Wall Street Journal-20080205-New Tests Spot Infectious Bugs More Quickly

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New Tests Spot Infectious Bugs More Quickly

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Hospitals are increasingly deploying a new breed of diagnostic tests -- ones that promise results in hours not days and are particularly effective in detecting deadly antibiotic-resistant "superbugs."

This new generation of tests identifies organisms using genetic information rather than growing them in a dish and examining them under the microscope. They can detect not only what strain of a bug is present more quickly than traditional tests, but also whether it is resistant to one antibiotic or vulnerable to another. The tests may even be able to identify some strains that can't be grown, and therefore couldn't be detected under the microscope.

That will go a long way in combating two of the biggest public- health concerns to emerge in recent years: the rapid spread of disease among increasingly mobile populations, and the evolution of "superbugs" resistant to existing medications. The tests are costlier than traditional tests and require hospitals to invest in expensive diagnostic equipment, but if they've been approved by the Food and Drug Administration, the tests are often covered by health insurers.

All this means that newly admitted hospital patients can avoid a prolonged wait-and-see routine in which doctors send cultures to the lab and await results, a process that can take a couple of days. Moreover, superbug carriers are detected and isolated faster; non- carriers avoid unnecessary -- and costly -- quarantines.

"We can determine the organism and the drug susceptibility and give early and appropriate therapy," says Richard Wenzel, president of the International Society for Infectious Diseases and chairman of the department of internal medicine at the Virginia Commonwealth University in Richmond.

Though the DNA-based molecular technology behind such tests has been around for years, their complexity at first relegated them to use primarily in academic and other sophisticated laboratories. But a number of easier-to-use commercially produced tests have hit the market.

Earlier this month the FDA added two more first-of-their-kind fast clinical tests to doctors' tool kits. One blood test diagnoses methicillin-resistant staphylococcus aureus -- the drug-resistant organism known as MSRA responsible for many hospital-acquired- infection deaths -- in just two hours, and the other is a panel of tests that can distinguish between 12 viruses and strains, including those responsible for common forms of the flu.

Molecular-based tests that have come on the market in recent years identify HIV, the virus that causes AIDS; chlamydia, a sexually transmitted disease; group B-streptococcus, the most common cause of blood infections in newborns; and avian flu.

"We're starting to see the FDA clear [tests] that are the whole kit in a box," says Christine Robinson, a virologist at the Children's Hospital in Aurora, Colo. "Like macaroni and cheese. Just add water."

While most rapid tests are found in hospitals, the hope is that one day doctors could run these tests in their offices, as they already can for strep throat using a different technology that detects the bug using antibodies or antigens.

Speedy tests may relieve doctors of the guesswork that takes place when they want to treat a patient before results come back from the lab, and reduce the likelihood that medications will be given inappropriately. And in hospitals, particularly in emergency-admission situations, these tests can help quickly identify contagious patients who need to be quarantined and relieve those who don't from enduring isolation.

Evanston Northwestern Healthcare, a system of three hospitals in Illinois, decided to go with a rapid-molecular test to screen all newly admitted patients for MRSA starting in August 2005. Isolating all new patients for several days was just too costly and time- consuming, says Lance Peterson, an Evanston epidemiologist who designed the screening program. Using a molecular MRSA test made by Franklin Lakes, N.J.-based BD (formerly Becton, Dickinson & Co.), on the other hand, results come back the same day patients' noses -- where MRSA hides out in carriers -- are swabbed.

"Most hospitals in the past have taken the tip-of-the-iceberg approach," Dr. Peterson says. "Isolating patients with MRSA infections and virtually ignore the patients who are colonized."

The first year of the surveillance program in the three Evanston hospitals led to a 13-fold decrease in MRSA transmission and an 80% reduction in MRSA blood infections compared with the two years before the screening was put in place, according to Dr. Peterson. The screening tests cost $600,000 for the year, and the increase in the number of patients who needed to be isolated cost an extra $44,000. But those amounts were offset by the estimated $1.2 million in medical costs saved by preventing 50 patients from being infected with MRSA.

The diagnostics field is "striving for ways to use innovation to do things that are faster, better, cheaper or preferably all three," says Patrick Balthrop, chief executive of Austin-based Luminex Corp., makers of a recently approved test "panel" -- a single test that covers an array of viruses.

Dr. Robinson, the Colorado virologist, says, "Physicians are demanding the tests. The pressure is on to do more and more."

Use of rapid molecular-diagnostic tests is still limited. The technology is costly and still considered relatively untested compared with the century-old diagnostic method of growing bacteria in petri dishes. Most companies sell their own equipment on which the tests must run, and the price tags are high -- from $20,000 to $70,000.

The tests are covered by a patient's insurer, but at around $30 a pop, they are still more expensive than traditional cell cultures, which cost about $3. And because the technique involves making copies of small segments of DNA, preparing the sample correctly and without contamination is important, yet not always easy, says Ben Kruskal, pediatrician and pediatric-infectious diseases specialist at Harvard Vanguard Medical Associates in Somerville, Mass.

Only several hundred hospitals use them, but that number is likely to grow. Changes in reimbursement structure -- such as Medicare's recent decision to stop paying for treatment that is the result of egregious medical errors, including hospital-acquired infections -- may increase the incentive, according to Bruce Jackson, a senior medical-technology analyst at RBC Capital.

The FDA has seen "steady growth" in the number of applications for approval of new tests, according to Steve Gutman, the FDA's director of the Office of In Vitro Diagnostics, Evaluation and Safety.

In the coming year, tests for tuberculosis and other drug-resistant bacteria are likely to be developed as well. Both Sunnyvale, Calif.- based Cepheid and BD plan this year to market tests for two more antibiotic-resistant superbugs, vancomycin-resistant enterococci and clostridium difficile, known as C. diff. The latter is considered the "next major infection challenge" in U.S. hospitals, says Betsy McCaughey, a health-policy expert and chairwoman of the Committee to Reduce Infection Deaths, a national health-care advocacy group. In 2006, it killed 4,000 people in hospitals in England, more than deaths attributable to MRSA in that country, she says.