Sample Sparing Assessment of Leukocyte Function Correlates With Sepsis Severity

Abstract

Dysregulated leukocyte responses underlie the pathobiology of sepsis, a leading cause of death; however, measures of leukocyte function are not routinely available for clinical care. Here, we developed an inertial microfluidic system for label-free isolation of leukocytes from microliter (50 uL) quantities of human peripheral blood to enable assessment of leukocyte phenotype and function in serial samples from hospitalized patients with sepsis (n=18) and healthy control subjects (n=10). Leukocytes in sepsis had significant increases in CD16dim and CD16- neutrophils, and CD16+ “intermediate” monocytes. Neutrophil elastase release, O2- production, and phagolysosome formation were significantly decreased with sepsis. Cellular activation in vivo was determined by tandem isodielectric separation and neutrophil Δ median isodielectric position (ΔmedIDP) was significantly changed with sepsis. With repeated sampling over 7 days, principal component analyses and mean Z-score of leukocyte phenotype and function were significantly more predictive of the clinical course in sepsis than CBC parameters. Together, these findings indicate that serial assessment of leukocyte function is feasible in microliter blood volumes and provides significantly more prognostic information than leukocyte counting.