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Rapid Results Pay Off for Patients and Healthcare Systems
Dr. Graeme Forrest was a man with a mission. Now practicing Infectious Diseases at the Portland VA, and Oregon Health & Science University in Portland, Dr. Forrest has been interested in the patient care and economic impacts of improving results delivery for several years. Back in 2004 at the University of Maryland, he pioneered the use of a computerized clinical decision support system to improve antibiotic utilization. No surprise, the system saved time and money.
Others have shown that rapid results delivery improves patient care and the bottom line,3–4 often by shortening overall length of stay. Barenfanger’s study showed $4 million on variable cost savings over a year with rapid reporting of identification and susceptibility results for all types of cultures. The PNA FISH dramatically shortened time to results over these earlier studies. As the University of Maryland’s laboratory under the direction of Dr. Richard Venezia implemented the technology, Dr. Forrest campaigned assertively to create a results-delivery system that would really make a difference on clinician behavior and then he went one step further: he measured the outcomes.5 The University of Maryland utilized their unique antimicrobial team, consisting of a dedicated clinical pharmacist, an infectious diseases attending, and infectious diseases fellows, to deliver the results of the PNA FISH assay. These assays have sensitivities and specificities that are virtually the same as culture,6 but the results are available within two hours if the tests are set up as soon as the gram stain from the bottle is shown to harbor gram-positive cocci in clusters. In most laboratories, the PNA FISH is set up once or twice a day, as in Venezia’s laboratory. The test is high-complexity, and requires a skilled clinical laboratory scientist to read the results on a fluorescent microscope. Because of several sample-handling steps, batch processing usually improves workflow. Even with results delivery occurring only daily, the hospital saw reduced utilization of vancomycin and projected cost savings of around $4000 per patient.
Cepheid’s GeneXpert® system MRSA/SA assay for blood culture broths (Xpert™ MRSA/SA BC) further reduces the time to results for blood cultures and has the essential added benefit of detecting not only Staphylococcus aureus, as the PNA FISH does, but also methicillin-resistant S. aureus (MRSA), which other current tests cannot do quickly and certainly not on a random access basis. In addition, Xpert MRSA/SA BC is the only molecular test with the FDA moderate complexity category. Laboratories using this system have the option of setting up each assay on a real-time basis as soon as the Gram stain has been read, perhaps by calling a laboratory assistant over to inoculate the cartridge and place it into the instrument. With only 1–2 minutes of hands-on time, the results are delivered to the screen in less than an hour. The screen result reads unambiguously “SA positive” (in red) or “SA negative” (in green) and “MRSA positive” (red) or “MRSA negative” (green). Wolk and colleagues recently published a six-center trial of this groundbreaking and accessible molecular assay.8 The sensitivity was 100% for S. aureus and 98.3% for MRSA in blood cultures for 406 blood cultures showing gram-positive cocci in clusters. In the near future, these results will interface easily with the laboratory’s LIS. We anticipate even more impressive patient care results and bottom line improvements with the use of this rapid and reliable new technology, even in laboratories strapped for personnel and whether they have the expertise to perform other molecular tests or not. Although MRSA is on the rise nationally, the percentage of blood cultures containing S. aureus that are resistant to the best anti-staphylococcal drugs (nafcillin, oxacillin, etc.) and actually require vancomycin, linezolid, clindamycin, or other antimicrobial agents active against MRSA is usually low. Of the blood cultures with staphylococci in the six-center study8, only 14% yielded MRSA. Results documenting the presence of MRSA or SA within one hour could dramatically and significantly reduce over-utilization of vancomycin and allow rapid placement of the most effective anti-staphylococcal antibiotic for each patient. Cost utilization studies for Xpert MRSA/SA BC are currently in progress. AdvanDx has now moved beyond Staphylococcus species into PNA FISH supported identification of yeast species and even gram-negative rods, such as E. coli, Acinetobacter and Pseudomonas aeruginosa. Dr. Graeme Forrest has already reported on savings associated with use of the PNA FISH yeast assay.9 The University of Maryland hospital showed >$1700 average savings per patient with candidemia associated with lower caspofungin utilization when C. albicans was identified quickly and the results included in patient care decisions with the consultation of a member of their antimicrobial team. An added benefit of the PNA FISH C. albicans test was that C. dubliniensis, otherwise very difficult to distinguish from C. albicans, did not hybridize to the C. albicans probe and was therefore identified correctly. AdvanDx is to be commended for an early and effective translation of a research tool to a clinical diagnostic assay. The company continues to forge ahead with unique new products that respond to clinical needs not currently being met by other products on the market. References
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At about that same time, Dr. Forrest heard about a new rapid protein-nucleic acid fluorescence in situ hybridization (PNA FISH) assay being developed by AdvanDx (Woburn, MA, now distributed by bioMerieux) to rapidly identify Staphylococcus aureus in blood cultures positive for gram-positive cocci in clusters. He immediately recognized the impact this information would have on early choice of appropriate therapy and more importantly, on physicians’ decisions whether even to begin therapy. As evidenced by many publications including a College of American Pathologists Q-Probe, most microbiology laboratories recover many more coagulase-negative staphylococci in blood cultures than S. aureus.1 In fact, fully half of all positive blood cultures may yield coagulase-negative staphylococci, many of which are procurement contaminants. Physicians often treat these “false positive” blood cultures, which costs the system money.2
According to Dr. Forrest, a key factor responsible for the success of this effort was that results were delivered by phone or face-to-face by a member of the trusted antimicrobial team. Ly and colleagues directly explored this possibility by randomizing which patients’ PNA FISH results would be called to clinicians.7 Their conclusions supported the hypothesis: the patients whose results were directly communicated to the clinician had reduced mortality (8% vs 17%) and showed a trend toward shorter hospital stays and reduced costs.7