Automated Hemogram Analyzer Parameters in Diagnosis of Sepsis/Infections

Application of robust diagnostic tools is pivotal for improving outcomes in sepsis management. High false-positive rates of sepsis screening tools remain a significant drawback. Microbiological culture, though considered the gold standard for diagnosing infections, typically takes 48–72 hours. Hence, recent research has focused on identifying reliable biomarkers, the most widely used being C-reactive protein, procalcitonin, and interleukin-6. Complete blood count (CBC) sample processing using automated hematology analyzers (AHA) can provide numerous parameters useful in the diagnosis of sepsis and act as sepsis biomarkers. Inflammatory states in sepsis dysregulate iron metabolism and induce oxidative damage to RBCs, thereby leading to red cell distribution width (RDW) elevation, making it a valuable prognostic marker. Neutrophilic leukocytosis, monocytosis, and eosinopenia are reported in early sepsis, while severe sepsis or organ dysfunction may be indicated by leukopenia, lymphopenia, and monocytopenia. Among the various CBC-derived ratios, the neutrophil-to-lymphocyte ratio (NLR) is the most commonly studied in the context of sepsis. Less commonly studied ratios include the monocyte-to-lymphocyte ratio (MLR), platelet-to-lymphocyte ratio (PLR), and platelet count-to-mean platelet volume ratio (PC/MPV). Cell population data (CPD) parameters in volume conductivity scatter (VCS) technology deranged in sepsis include increased mean neutrophil volume (MNV), mean monocyte volume (MMV), and volume distribution width (VDW), while mean neutrophil scatter (MNS) values are generally decreased. Monocyte distribution width (MDW), an emerging biomarker, reflects the heterogeneity in monocytes’ size. Similarly, various leucocyte CPD generated by fluorescence flow cytometry also provide valuable information. The delta neutrophil index (DNI) reflects the immature granulocyte fraction in peripheral blood. Thrombocytopenia is a common finding in sepsis. Elevated mean platelet volume (MPV), platelet distribution width (PDW), and immature platelet fraction (IPF), which reflect increased platelet turnover, serve as potential biomarkers for early sepsis detection and severity assessment. Modern hematology analyzers generate novel research parameters to detect various infections. High fluorescence lymphocyte count (HFLC) is a valuable marker for distinguishing dengue from other febrile illnesses. In COVID-19, markers such as lymphopenia, neutrophilia, elevated NLR, eosinopenia, and CPD parameters like MDW and lymphocyte cell size and the width of dispersion (LY-WZ) provide insights into disease severity. Hemogram analyzers can detect malaria-infected RBCs directly using multi-angle polarized scatter separation (MAPSS) or fluorescence flow cytometry, or indirectly by identifying hallmark scattergram abnormalities.