How Do Rapid Diagnostic Tools Impact Patient Outcomes?


Jerod Nagel, PharmD, highlights how rapid diagnostic tools can be utilized in antibiotic stewardship programs to improve outcomes for patients with S. aureus.

There are many commercially available rapid diagnostic tools that allow for early detection of infection. With early detection, healthcare practitioners everywhere hope to improve patient outcomes by linking them with appropriate treatment as quickly as possible.

At the Society of Infectious Diseases Pharmacists (SIDP) Program at ASM Microbe Society Day in New Orleans, Louisiana, Jerod Nagel, PharmD, infectious disease specialist at the University of Michigan Hospital and Health System, presented his team’s findings. He provided all members in attendance with an overview of such diagnostics, as well as how to incorporate them into effective antimicrobial stewardship programs in healthcare facilities, in order to reach that end goal—improving patient outcomes.

In his presentation, Dr. Nagel specifically focused on Staphylococcus aureus infections. “We all know it’s a huge problem,” he said, pointing out that it ranks number one on the list of pathogen-associated hospital-associated infections (HAIs). Not surprisingly, when considering the burden of S. aureus bacteremia, there is high morbidity and mortality.

“There’s 15% mortality, about 10% to 20% of those patients have deep-seated endocarditis or other metastatic disease, a lot of these patients have to go to the ICU [intensive care unit], the length of stay is incredibly long (10-20 days), and about half of the patients get an ID [identification and detection] consult,” he explained.

Dr. Nagel proceeded to share data showing that there was a significant reduction in mortality and length of hospital stay among patients who received early therapy for S. aureus bacteremia. “So, that brings us to talking about what we could do to get patients on the right antibiotics right away,” he said.

Part of the answer lies in the new technologies available for rapid ID of these organisms. Here are the following rapid diagnostic tools that Dr. Nagel highlighted in his talk:

Mass spectrometry / [Matrix-Associated Laser Desorption/Ionization-Time Of Flight] MALDI-TOF: MALDI-TOF utilizes mass spectrometry and “identifies bacteria based on unique protein sequences.” It reduces the time to organism ID by 24-36 hours—it takes about an hour. Unlike some of the other available tools, it can replace conventional or automated systems for organism ID for most organisms. It has a low reagent cost, but still makes for a costly initial investment, according to Dr. Nagel. Disadvantage? It’s “currently limited clinical utility in detecting methicillin resistance.” Regardless, it is commonly used in Europe but is also gaining popularity within the United States.

Nucleic acid hybridization / PNA-FISH, Quick-FISH, Xpress-FISH: One of the biggest advantages of Quick-FISH is the extremely rapid testing process—it only takes about 20 minutes. This is one of the first products that came out, and as a result, many hospitals have clinical experience with this product. Not only that, but “it has proven benefit,” Dr. Nagel said. However, the initial product is limited to 3 targets, where other multiplex platforms have many more. It is also limited when it comes to detecting resistance mechanisms.

Nucleic acid amplification / Nanosphere Verigene: This testing process takes between 1 to 2 hours. It is multiplex technology, which means that you can know an organism ID and select resistance genes at the same time. You can also “escalate or de-escalate therapy for Staphylococcus.” Drawbacks? It’s an add-on product, so it doesn’t replace any current technology being used for organism ID or susceptibility. Dr. Nagel added that, with this product, there is also “diminished sensitivity and specificity directly from specimens.”

Accelerate: Accelerate is “one of the newer technologies that’s coming out, which is pretty novel, kind of outside-the-box thinking.” It’s also the only product to offer “rapid organism ID, [minimal inhibitory concentration] MICs, and sensitivities” which tracks the growing curve, division rate, time/effect curve, and gages expected patterns. “If we’re talking S. aureus, you would know the organism ID in 20 minutes and then the MIC and susceptibilities about 7 hours later.” However, it’s not capable of handling a large number of samples, because there are not too many antibiotics on panel. Therefore, compared with other technologies, it’s slower in detecting methicillin-resistance.

“[With these tools], you’re going to get data quicker, [there’s] improved time to optimal therapy, [you’re] reducing length of stay, [and] reducing mortality. But, I think one of the things that we’re facing now is [the question of] how [to] manage the patient as a whole, and how [to] incorporate rapid diagnostics into that scenario,” Dr. Nagel said.

Even with early targeted therapy brought on by early detection, morbidity and mortality “remains significant.” Therefore, improvements need to be made in other areas, such as: surgical management, antibiotic regimens, medical management, and identification of complicated bacteremia, among others.

Dr. Nagel stressed that patient care should be in compliance with performance measures that are listed in the Infectious Diseases Society of America (IDSA) guidelines. At his facility, Dr. Nagel and his team have come up with a collaborative approach to improving outcomes for those with S. aureus bacteremia. For example, for one part of their approach they “have a process where if we have [gram-positive Cocci] GPC in clusters, we have a pharmacist receive a real-time alert 24/7, and so, if patients aren’t on the right therapy we can get them on the right therapy.” They also provide ID consultations to all of [their] patients. “I think the data is overwhelmingly positive for patients having good outcomes from ID consultations,” he added. They also ensure that other measures are being met, for example, is the patient receiving therapy for the right duration? The researchers even created cards to give out to ID fellows that provided guidance on treatment duration and how to handle somewhat controversial issues. The results? Compliance to guidelines significantly improved—going from 56% up to 84%.

“Rapid diagnostics can dramatically improve time to organism identification and detection of some resistance genes. Developing a process to facilitate timely antibiotic changes following rapid diagnostics is essential, and then developing a comprehensive approach can optimize [patient] outcomes,” Dr. Nagel concluded.

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