A Pilot Study Assessing the Utility of Quantitative Myeloid-Derived Suppressor Cell Measurements in Detecting Posttraumatic Infection.

Objectives: Biomarkers that facilitate earlier diagnosis of posttraumatic infection could improve outcomes by expediting treatment and mitigating complications, including sepsis. We hypothesized that circulating myeloid-derived suppressor cell (MDSC) counts could identify patients with posttraumatic infection.

Design setting and patients: We conducted a single-center, prospective observational pilot study of trauma victims who required greater than or equal to 48 hours of mechanical ventilation. Whole blood was collected and tested by flow cytometry.

Interventions: None.

Measurements and main results: Samples were analyzed in real-time with an 11-parameter quantitative MDSC assay. Two physician adjudications of infection were performed through a blinded review of medical records. MDSC and other cell counts were compared between subjects with and without posttraumatic infection using non-parametric methods. Data are presented as medians (25th-75th percentile). The area under the receiver operating characteristic (ROC) curves were used to assess the accuracy of cell counts for diagnosing infection. Most subjects (n = 39) were male (79%) with a median age of 48 (interquartile range [IQR] 32-65), Injury Severity Score of 29 (IQR 21-41), and ICU length of stay of 13 days (IQR 8-19). Twenty-one (54%) developed an infection and 11 (28%) of the cohort died. We compared total MDSC (T-MDSC) counts closest to the day of infection diagnosis with the initial T-MDSC counts in subjects without infection. T-MDSC counts were higher in those with infection compared to those without infection (696 [368-974] and 304 [181-404] cells/μL, respectively; p < 0.001). Lymphocyte, neutrophil, and CD45+ leukocyte counts were not statistically different between the groups. The area under the ROC curve distinguishing those with infection from those without for T-MDSC was 0.83 (p < 0.001).

Conclusions: MDSC counts determined by quantitative whole blood flow cytometrics can detect posttraumatic infection and may be useful to guide further diagnostic testing in critically ill trauma victims.