NEW YORK (360Dx) – A point-of-care test that monitors the immune system's response without requiring manual processing could help clinicians treating sepsis, a condition that should be quickly detected to provide an optimal clinical effect, according to the test's developers at the University of Illinois and the Carle Foundation Hospital in Urbana, Illinois.
To monitor the immune system's response during infection or inflammation, the test looks for an increase in the expression of the CD64 protein marker on specific types of white blood cells called neutrophils.
Using 10 microliters of whole blood, a microfluidic biochip counts white blood cells and measures CD64 on the neutrophils' surfaces. Levels of CD64 surge as the patient's immune system responds to the infection, the researchers said.
They used the point-of-care microfluidic chip in clinical studies at the Carle Foundation Hospital leveraging blood samples from patients who were systemic inflammatory response syndrome-, or SIRS-, positive, or had blood cultures ordered at the time of admission, or both.
The researchers published their findings on Monday in the journal Nature Communications.
In the paper, they wrote that they used "differential immunoaffinity capture technology to electrically quantify antigen expression level on the CD64+ cells."
The test can help doctors identify sepsis at its onset and monitor infected patients, and it could point to a prognosis, Rashid Bashir, a professor of bioengineering at the University of Illinois and the research team leader, said in a statement.
"We are looking at the immune response, rather than focusing on identifying the source of the infection," Bashir said.
He noted that the test can complement existing diagnostic tests that enable detecting and identifying bacteria, and added that "We think we need both approaches: detect the pathogen, but also monitor the immune response."
Sepsis is among the most serious and life-threatening problems in the intensive care unit. The body's immune system releases chemicals that fight sepsis, but it can also produce widespread inflammation that can rapidly lead to organ failure and death for the patient.
The infection affects roughly 20 percent of patients admitted to hospital intensive care units, yet it is difficult to predict the inflammatory response in time to prevent organ failure, said Karen White, an intensive care physician at Carle Foundation Hospital, who led the clinical study.
White noted that the infection can become life-threatening quickly, "so a bedside test that can monitor [a] patient's inflammatory status in real time would help us treat it sooner with better accuracy."
Doctors routinely detect sepsis infection by monitoring patients' vital signs — including their blood pressure, oxygen levels, and temperature. The work to identify the source of the infection using blood-culture and other tests often can take days, which is time the patient might not have, the researchers said.
Clinicians use hematology analyzers for complete blood cell counts and flow cytometers for specific leukocyte counting and to perform antigen expression-based cell quantification. Lack of standardization has hampered the adoption of flow cytometers at the point of care, the researchers said, adding that flow cytometry measurement and hematology testing require "both a well-equipped laboratory and significant technical expertise, which are impossible to maintain 24/7 in ICUs."
In their clinical study, the developers tested their device with blood samples taken from Carle Foundation Hospital patients in the ICU and emergency room. They monitored CD64 levels over time and correlated them with the patient's vital signs. They found that their rapid-test results correlated well with results from traditional tests.
The researchers said that they are also working to incorporate measurements for inflammation markers other than CD64 into the rapid-testing device to give a more complete picture of the body's response, and to enable earlier detection.
"We want to move the diagnosis point backward in time," Bashir said. "The big challenge in sepsis is that no one knows when you get infected. Usually you go to the hospital when you already feel sick." He said that the goal is to someday enable patients to test for sepsis at home and detect it before they feel sick enough to go to the hospital.
In their research paper, the team noted that they have "shown the biochip’s utility for improved sepsis diagnosis" by combining its measurements with electronic medical records.
Developing a point-of-care system for early stratification of sepsis "will have a significant impact on patients and hospitals, as delay in the early diagnosis of sepsis can have multiple drawbacks," the researchers wrote.
Apart from potentially improving screening techniques and providing a greater choice of therapeutic options, they said, this type of system could "reduce lengthy stays in critical care units, priced at [greater than] $20,000 per stay on average for septic patients in the US."
They have launched a startup company, Prenosis, to commercialize the test.