Rapid Molecular Test Identifies Sepsis Patients Most Likely to Have Positive Blood Cultures

Sepsis is caused by a patient’s overwhelming immune response to an infection. If undetected or left untreated, sepsis leads to tissue damage, organ failure, permanent disability, and often death. Around the world, physicians struggle to rapidly and reliably identify sepsis due to the lack of adequate diagnostic tools. Blood cultures remain a cornerstone of sepsis management, yet are frequently negative, delayed, or contaminated. Now, new study findings highlight a strong association between a patient's sepsis risk and likelihood of positive cultures, with a molecular test delivering results just 90 minutes after a blood draw.

Immunexpress (Brisbane, Australia) pioneers technology that rapidly detects sepsis by analyzing the patient's immune response, marking a paradigm shift away from traditional pathogen-detection methods. The company’s SeptiCyte RAPID is a sample-to-answer, cartridge-based, host response molecular test for sepsis using reverse transcription polymerase chain reaction (RT-PCR) to quantify the relative expression of two host response genes (PLAC8 and PLA2G7) from whole blood.

SeptiCyte RAPID generates a SeptiScore within approximately one hour, reported across four interpretation bands reflecting increasing likelihood of sepsis. SeptiCyte RAPID runs on the Biocartis Idylla platform and is intended for use in conjunction with clinical assessments, vital signs, and other laboratory findings as an aid in differentiating infection-positive sepsis from non-infectious systemic inflammation.

The latest study was a post-hoc retrospective analysis of data from three prospective observational cohorts encompassing North America, Europe, and sub-Saharan Africa. The analysis included 506 critically ill and acute care patients, with sepsis independently adjudicated and blinded to SeptiCyte RAPID results.

The findings, published in Journal of Clinical Medicine, show that higher SeptiScores were strongly associated with blood culture positivity, with >90% of blood culture–positive sepsis patients falling into the highest SeptiScore bands. No blood culture–positive sepsis cases were observed in the lowest SeptiScore band, highlighting the test' ability to identify patients at very low likelihood of sepsis.

Diagnostic performance was strong, with an AUC of 0.91 for distinguishing blood culture–positive sepsis from non-infectious systemic inflammation (SIRS). Importantly, binary cut-point analyses demonstrated 100% sensitivity at low SeptiScores (<5.0) and 100% specificity at high SeptiScores (>11.4) within this dataset, underscoring the potential clinical utility of SeptiCyte RAPID as an early risk-stratification tool.

"The study findings suggest that SeptiCyte RAPID, when used alongside clinical assessment, may help clinicians prioritize which patients are most likely to benefit from blood cultures, interpret equivocal results, and potentially reduce unnecessary testing," stated Dr. Maik von der Forst from the Heidelberg University Hospital Germany. "There is a need for tools that guide the use of microbiologic diagnostics in the hospital and especially in resource-constrained healthcare settings, emergency departments, and ICUs."

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