Clinical outcome of critically ill patients cannot be defined by cutoff values of monocyte human leukocyte antigen-DR expression.

Septic shock is the most common cause of death in intensive care units. During the last two decades, new strategies have focused on the diagnosis and on the immunological changes in critically ill patients. There have been conflicting reports whether monocyte human leukocyte antigen (HLA) DR expression poses a useful parameter to characterize clinical outcome of these patients. To elucidate the role of monocyte HLA-DR expression, we hypothesized that low expression of HLA-DR on circulating human monocytes in critically ill patients correlates with higher mortality and that cutoff values of HLA-DR discriminate surviving from nonsurviving patients. In this retrospective study, monocyte HLA-DR expression in 413 critically ill patients was investigated during their intensive care unit stay. Human leukocyte antigen DR was determined in a quantitative and standardized procedure by flow cytometry (anti-HLA-DR monoclonal antibodies bound per cell [mABs/cell]) at least every third day or when clinical changes in the patients conditions were observed. Healthy probands served as control group to determine the range of "normal" values. As expected, HLA-DR expression was significantly higher in the group of survivors (n = 279) than in the group of nonsurvivors (n = 134; mABs/cell: 23,038 [SD, 11,150] vs. 18,070 [SD, 8,906]; P < 0.001). When minimal HLA-DR values per patient were compared, no cutoff values could be identified between the groups of survivors and nonsurvivors (mABs/cell: 19,611 [SD, 11,129] vs. 14,944 [SD, 8,013]; P < 0.001). In conclusion, in this sizable cohort we could again show that HLA-DR expression is decreased in critically ill patients but it is not suitable as a prognostic or predictive parameter for clinical outcome.