Summary
Newer sepsis diagnostics, including monocyte distribution width (MDW), Intellisep, and MeMed BV, show promise in clinical studies but have limitations. MDW, available on the Beckman Coulter platform, is predictive of sepsis when used with white blood cell count but has low sensitivity and specificity. Intellisep, a rapid cellular host-response diagnostic, demonstrates good sensitivity and specificity in identifying sepsis risk and potential prognostic value, though it requires a dedicated instrument and physician heuristics.
Charna Albert
March 2026—Newer methods for detecting sepsis have performed well in clinical studies, though each has its limitations and there is no comparison study from which a winner could emerge.
“They’re so different that I don’t think we’re in a place where we can say which assay is best. They’ll probably have different use cases,” said Christopher Farnsworth, PhD, D(ABCC), in an ADLM session on sepsis last summer.
In the emergency department at Barnes-Jewish Hospital, where Dr. Farnsworth is medical director of clinical chemistry and point-of-care testing, patients in danger of becoming septic are monitored using a list of criteria, such as a SOFA score of greater than two, so they can be moved to testing and treatment pathways. For now, the hospital system is not using in clinical practice any of the novel sepsis diagnostics that have emerged in recent years. “But we are watching very carefully,” says Dr. Farnsworth, professor of pathology and immunology and of emergency medicine at Washington University in St. Louis.
Sepsis is a heterogeneous syndrome with multiple phenotypes, and each phenotype presents with different elevations in biomarkers. Thus, there’s little chance that a single biomarker could do the job. To complicate matters, “some of these technologies have very different claims that we have to be aware of as well and be ready to adjust to as laboratorians,” said Dr. Farnsworth, who, in the ADLM session, walked through three groups of candidate biomarkers: cell-, protein-, and gene-expression–based methods.
Monocyte distribution width, a cell-based marker, is not new, Dr. Farnsworth noted. In sepsis, immune dysregulation activates the monocyte population, giving the cells an elongated appearance. “You’re going to have variation about the width of these monocytes, which is what the assay is picking up,” he said. The Food and Drug Administration-cleared indication for the assay is as an aid in identifying patients with sepsis or at increased risk of developing sepsis within the first 12 hours of hospital admission.
A study at three academic medical centers found an MDW greater than 20 U (with or without white blood cell count) is effective for sepsis detection during an initial ED encounter. The take-home from this study and another, Dr. Farnsworth said, is that MDW is more predictive of sepsis when used together with white blood cell count (Crouser ED, et al. Chest. 2017; 152[3]:518–526; Crouser ED, et al. Crit Care Med. 2019;47[8]:1018–1025). “If you do have it in conjunction with white blood cells, you can potentially use it as a screening tool to try to move patients toward a particular pathway,” he said. “So the clinical studies use it as a true screening test, with a high positive likelihood ratio.”
The marker doesn’t require physician heuristics, he noted, as MDW is reported (on the Beckman Coulter platform) as a component of the CBC with differential. Some studies have shown that time to lactate is a mortality predictor. “When I talk to my ED physicians, one of their pain points is they aren’t necessarily suspecting sepsis, so they don’t order the lactate right away or administer antibiotics,” he said. “This could, potentially, in a completely agnostic way—because you’re getting it with every single CBC—tell you that this patient is potentially septic, and then you can start going down that route and get them antibiotics.”