The One-Hour Sepsis Test: A Diagnostic Revolution in Critical Care

CHICAGO, IL – March 23, 2026 – In the high-stakes environment of a hospital's critical care unit, every minute counts. For patients with sepsis—a life-threatening condition where the body's response to an infection damages its own tissues—the race against time is particularly stark. For decades, clinicians have relied on blood cultures, a diagnostic process that, while essential, can take 12 to 24 hours or more to yield results. Now, a shift in diagnostic strategy is gaining momentum, promising to give doctors a crucial head start.

This week, at the Society of Critical Care Medicine (SCCM) 2026 Critical Care Congress, molecular diagnostics company Immunexpress is highlighting new data on its SeptiCyte® RAPID test, a tool that can determine the likelihood of sepsis from a blood sample in approximately one hour. The findings suggest a new frontier in managing one of medicine's deadliest and most elusive conditions.

The Race Against the Clock in Sepsis Care

Sepsis is not a specific disease but a syndrome, a cascade of dysregulated immune responses to infection that can lead to organ failure and death. Its initial symptoms—fever, rapid heart rate, confusion—are non-specific and can mimic less severe conditions. This diagnostic ambiguity forces a difficult choice on physicians: start broad-spectrum antibiotics immediately, risking overuse and contributing to antimicrobial resistance, or wait for confirmation, losing precious time that could cost the patient their life.

The traditional gold standard, blood culture, aims to grow and identify the causative pathogen. While vital for tailoring antibiotic therapy, its inherent delay creates a dangerous diagnostic gap. This has spurred a search for faster methods, leading to the development of host-response diagnostics. Instead of searching for the invading pathogen, these tests analyze the patient's own immune system, measuring specific genetic or protein biomarkers to see if the body is mounting the chaotic response characteristic of sepsis.

A New Tool in the Diagnostic Arsenal

Immunexpress's SeptiCyte® RAPID is at the forefront of this new approach. The sample-to-answer test uses reverse transcription polymerase chain reaction (RT-PCR) to measure the expression of two specific host genes, PLAC8 and PLA2G7, from a whole blood sample. The result is a single number, the SeptiScore®, which indicates the likelihood that a patient with signs of systemic inflammation has sepsis.

At the SCCM Congress, Immunexpress's Chief Medical Officer, Dr. Roy Davis, presented data showing a strong correlation between a high SeptiScore® and patients who are later confirmed to have sepsis via a positive blood culture. The data, from a retrospective analysis of over a thousand patients, showed the test aligned with physician-adjudicated, blood-culture-positive sepsis cases 91% of the time. Furthermore, the test demonstrated a high degree of accuracy (an Area Under the Curve, or AUC, of 0.91) in distinguishing these septic patients from those with non-infectious systemic inflammation (SIRS).

This ability to provide a clear, actionable result within an hour—long before blood culture results are available—is the test's defining feature. It allows clinical teams to triage patients more effectively, focusing resources and aggressive treatments on those most likely to have sepsis while potentially de-escalating care for others.

Impact on Stewardship and High-Risk Patients

The implications of rapid, accurate sepsis differentiation extend beyond the initial diagnosis. One of the most significant benefits is its potential impact on antibiotic stewardship. By providing a strong indication that a patient's inflammation is not due to a bacterial infection, the test can give clinicians the confidence to withhold or discontinue unnecessary antibiotics. This is a critical tool in the global fight against antimicrobial resistance (AMR).

The test's utility is particularly pronounced in complex and immunocompromised patient populations, who are both highly susceptible to infection and prone to non-infectious inflammatory events. A recent publication highlighted SeptiCyte RAPID's strong performance in hematological malignancy patients with neutropenic fever, a common and challenging clinical scenario. In this group, the test showed an AUC of 0.84 for distinguishing infectious from non-infectious fever, suggesting it can provide crucial clarity in some of the sickest patients.

"Enhanced diagnostic precision facilitates earlier antimicrobial decisions, reduces unnecessary antibiotic exposure, and improves stewardship practices in high-risk immunocompromised populations, including patients post bone marrow transplant with neutropenia," stated Dr. Roy Davis. "Furthermore, the rapid 1 hour turnaround time for a SeptiCyte result is obtained 12 – 24 hours ahead of blood culture results helping to guide earlier clinical decision making."

The Path to Clinical Adoption

Immunexpress is not alone in the quest for a better sepsis diagnostic. The market is becoming increasingly competitive, with companies like Inflammatix, Cytovale, and Abionic also bringing FDA-cleared rapid tests to market, each using different technologies—from multi-gene expression panels to the biophysical properties of immune cells—to tackle the same problem. This burgeoning competition signals a significant shift in clinical practice, as regulatory bodies and healthcare systems recognize the urgent need for innovation.

A key factor in the practical adoption of any new diagnostic is its ease of use. SeptiCyte® RAPID runs on the Biocartis Idylla™ platform, a fully automated system that requires minimal hands-on time from lab technicians. This cartridge-based, sample-to-answer format is designed for easy integration into existing hospital laboratory workflows, a crucial feature for widespread adoption. With over 2,000 Idylla™ instruments already installed globally, Immunexpress has a clear pathway for commercial expansion.

Having received FDA clearance in late 2021 and a CE Mark in Europe, the test is already being implemented in clinical settings. Hospitals like FirstHealth of the Carolinas have integrated it into their sepsis protocols, citing its ease of use and its role in helping identify true sepsis cases earlier. As more institutions gain experience with rapid host-response diagnostics, their role in the standard of care is likely to become more defined, potentially finding a place in updated guidelines from organizations like the Surviving Sepsis Campaign.

While these rapid tests will not replace the need for pathogen identification through blood cultures, they are poised to fundamentally restructure the initial phase of sepsis evaluation. By providing an immediate assessment of the host's immune response, they arm clinicians with critical information during the first, most decisive hour of care, transforming the diagnostic race against the clock into one they are better equipped to win.