Analysis of peripheral blood lymphocyte subsets in critical patients at ICU admission: A preliminary investigation of their role in the prediction of sepsis during ICU stay

A better knowledge of factors predicting the development of sepsis in patients hospitalized in intensive care unit (ICU) might help deploy more targeted preventive and therapeutic strategies. In addition to the known clinical and demographic predictors of septic syndromes, in this study, we investigated whether measuring T and B lymphocyte subsets upon admission in the ICU may help individualize the prediction of ensuing sepsis during ICU stay. Between May 2015 and December 2016, we performed a prospective cohort study evaluating peripheral blood lymphocyte T-CD4+ (T-helper cells), T-CD8+ (cytotoxic T-cells), T-CD56 + (natural killer cells), and T-CD19+ (B-lymphocytes), using flow cytometry on blood samples collected 2 days after admission in the ICU. We enrolled 176 patients, 65.3% males, with mean age of 61.1 ± 15.4 years. At univariate analyses, higher percentages of CD19 B-cells were significantly associated with ensuing sepsis (20.5% (15.7–27.7)% vs 16.9% (11.3–22)%, P = 0.0001), whereas median interquartile range (IQR) proportions of CD4 T-cells (41.2% (33.4–50.6)% vs 40% (35–47)%, P = 0.5), CD8 T-cells (21.1% (15.8–28.2)% vs 19.6% (14.6–25.1)%, P = 0.2) and CD56 T-cells (1.7% (0.9–3.1)% vs 1.45% (0.7–2.3)%, P = 0.4) did not reveal any significant association. An unexpected, highly significant inverse correlation of CD8 T-cells and CD19 B-cells proportions, however, was observed, suggesting that patients with lower CD19 and higher CD8 proportions might be somehow protected from ensuing sepsis. We therefore studied the ability of the CD8/CD19 ratio to predict ensuing sepsis in our sample. In final models of multivariate logistic regression, the following independent associations were found: previous antibiotic exposure (odds ratio (OR): 3.8 (95% confidence interval (CI): 1.35–10.87), P = 0.01), isolation of at least one multi-drug resistant organism at any time during ICU stay (OR: 8.4 (95% CI: 3.47–20.6), P < 0.0001), decreasing age (OR: 0.9 (95% CI: 0.93–0.99), P = 0.02) and a CD8/CD19 ratio >2.2 (OR: 10.3 (95% CI: 1.91–55.36), P = 0.007). Our data provide preliminary evidence that immune characterization of critically ill patients on ICU admission may help personalize the prediction of ensuing sepsis during their ICU stay. Further polycentric evaluation of the true potential of this new tool is warranted.