A simple test in use at the Univer-sity of Maryland Medical Center that in hours can identify specific gram-positive bacteria and yeast directly from positive blood cultures is reducing patient mortality, cutting the length of hospital stays, saving money and potentially decreasing the likelihood of antibiotic resistance.
Published studies conducted at the medical center show that using PNA FISH testing rather than traditional agar/phenotypic methods to identify Candida albicans resulted in an overall cost savings of $1,729 per infected patient and a reduction in the use of caspofungin, says Richard Venezia, medical center lab director and professor at the University of Maryland School of Medicine.
Additionally, using the test to rule out Staphylococcus aureus on positive blood cultures saved about $4,000 per patient, cut median hospital stays by about two days and reduced the use of vancomycin.
“In terms of reducing the time a patient spends in the hospital, outside of the intensive care units, this has had an impact,” Venezia says. “In terms of pharmaceutical costs, this has had an impact. In terms of patient outcome and patient care, it’s had an impact. In terms of my budget, it’s increased my budget in the laboratory. But that’s just one cost compared with the total cost of savings.”
Other savings and benefits obtained at the 689-bed medical center are more difficult to measure, he says. “We couldn’t address the decrease in nursing time—in other words, if a physician doesn’t order more tests, the nurse doesn’t have to collect more specimens. If a physician doesn’t say, ‘Let’s pull the lines and put new intravenous lines in because these old ones might be infected,’ that saves time and reduces the risk for a patient,” Venezia says.
Because information from the test speeds up the ability to prescribe directed and more effective medication sooner, a patient’s time in recovery and in the hospital usually decreases, he says.
This means better use of resources because fewer tests are ordered and fewer catheters and other such materials are used, pharmaceutical costs decrease and busy staff can use their time more effectively. It also spares patients from taking medication they do not need.
“We couldn’t put a number on antibiotic resistance,” Venezia says. “But we felt that if we decreased the unnecessary use of a certain antibiotic, then theoretically we should decrease the incidence of resistance to that antibiotic. If you use an antibiotic directed at the infecting agent more quickly, you decrease the use of broad spectrum antibiotics. I think everyone pretty much agrees that it should decrease resistance.”
The PNA FISH test was developed by AdvanDx Inc., based in Woburn, Mass. It uses fluorescence in situ hybridization (FISH) with peptide nucleic acid (PNA) probes to identify gram-positive bacteria and yeast within three hours of a primary blood culture turning positive, says Philip Onigman, a director at AdvanDx. The test, which comes as a kit of four chemicals, was approved by the FDA in 2003.
“It’s a molecular, chemistry-based test that works by looking at cells with a fluorescence microscope,” Onigman says. The kit works with any fluorescence microscope and on any blood culture instrument and is designed so that staff in a microbiology lab can read the results.
Every year, 350,000 patients in the United States acquire bloodstream infections and more than 90,000 die, Onigman says. Initial blood cultures identify only the broad class of these infections, he says. Using traditional culture colony methods to identify the species can take up to 72 hours, at a cost of $1 to $15.
The PNA FISH costs between $20 and $45 depending on whether testing is done in batches, but it takes only three hours or less to correctly identify the species.
The sooner doctors know the species, the faster they can prescribe effective medication, or alter treatment if the test shows culture contamination, he says.
Treating patients with antibiotics because of false positive blood cultures reduces their normal bacteria and potentially makes them more susceptible to infection by resistant organisms.
By fixing that, hospitals have been able to send some patients home earlier or to get them out of the intensive care unit several days earlier and halt unnecessary therapies. As a result, finance and materials management staff have been able to measure that a higher annual investment in the lab is saving money overall by cutting pharmacy costs and improving hospital efficiency, Onigman says.
“But it takes compliance by physicians and it takes management and it takes some education,” he says.
A midsized hospital typically might spend $50,000 to $100,000 annually on PNA FISH testing, but the corrections in patient care that they make as a result of the testing can easily save several million dollars, Onigman says.
Some hospitals report that the PNA FISH test is 100 percent sensitive and specific, Onigman says. Traditional follow-up testing still occurs, primarily to learn more about a species’ antibiotic susceptibility profile, something that the PNA FISH test does not measure.
However, they will know the most likely antibiotic susceptibility profile based on the history in their hospital for that organism because they will have laboratory reports on those statistics.
When running studies on the PNA FISH test at the Maryland Medical Center, staff knew already from other hospital reviews that the test was accurate, Venezia says.
“Our approach was: How does it affect the clinician? How does it affect the bottom line of the hospital? How does it affect patient care?” Rough data then was sent to the hospital fiscal department for number crunching. The results showed improved patient care and lower costs overall.
Published hospital studies showed that the rapid identification of Candida albicans resulted in a significant reduction of the use of caspofungin, a broad spectrum antifungal, and that despite an increase in the use of fluconazole, in one year the hospital saved $130,000, Venezia says.
Another study showed that the differentiation of S. aureus from coagulase-negative staphylococci in blood cultures reduced vancomycin use and the median length of time patients stayed in the hospital by about two days. During the three-month study, the hospital saved about $110,000 by targeting medication faster, he says.
“We always think of S. aureus as causing an infection. Therefore, we have to treat it,” he says. Identification can take a couple of days using traditional testing methods.
While waiting for the results, physicians prescribe broad spectrum medication. When hospital residents learned about the study findings, they began calling the lab for PNA FISH test results.
“For a physician to ask for something, it has to be helpful,” he says. “They’ve got so much to do, the last thing they want to do is get on the phone and ask for information they don’t need to know.”
Figures on mortality rates still are undergoing analysis, but a decrease is evident, Venezia says.
“Anytime you start a patient on an antibiotic that you know worked earlier, you are going to decrease the chance of a bad outcome,” he says. “A corresponding decrease in the number of tests ordered, nursing time and everything that goes with targeting treatment faster was presumed but not formally documented in our study.”
Startup costs are minimal because most labs already have a fluorescent microscope and a water bath, and savings reaped from using the test can offset outlays by tenfold or more. “What you might need is a different lens filter to see the fluorescent. So, the cost might run about $1,000,” he says.
“You don’t have to do much training because most of the technologists in the laboratory already read morphology off gram stains and read fluorescents in other types of tests.”
Gaining widespread approval for and acceptance of the new test method means talking not only to lab supervisors or pathologists, but to physicians and clinicians, hospital administrators, quality assurance and infection control personnel, medical directors and materials management teams, he says.
It means looking at the big picture. “The laboratory has to get out of the mindset that, ‘My budget is the only budget I care about. They now have to think in terms of whether budget increases, in proportion to the positive effect on the total budget of the institution, becomes insignificant,” Venezia says.
“Not many administrators allow their laboratory to do that. And that’s the point that has to come across.”
Nancy Torner is a freelance writer based in Roseville, Minn.
PNA FISH assay effect on length of stay and defined daily doses (DDD) of vancomycin use in patients not in intensive care units
| Control group | PNA FISH | Probability value | |
| Total DDD of vancomycin per patient | 6.78 | 4.9 | NS* |
| DDD of vancomycin per patient after gram-positive cocci in clusters (GPCC) | 4.8 | 2.55 | 0.06 |
| Patients receiving no doses of vancomycin | 3/34 | 9/53 | 0.06 |
| (9%) | (17%) | NS | |
| Patients receiving one or fewer doses of vancomycin | 5/34 | 23/53 | <0.005 |
| (15%) | (43%) | ||
| Number of patients with length of stay <3 days after GPCC | 6/34 | 20/53 | 0.006 |
| (18%) | (38%) | NS | |
| Median length of stay (days) | 6 | 4 | <0.05, CI* |
| 0.95-1.87 |
*NS = Not significant; CI = chronically infected
Source: Journal of Antimicrobial Chemotherapy, May 2006
This article first appeared in the December 2007 issue of Materials Management in Health Care.
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