Improvement in detecting bacterial infection in lower respiratory tract infections using the Intensive Care Infection Score (ICIS)

Abstract Background: Immediate treatment of lower respiratory tract infections (LRTI) caused by bacteria is important to reduce pneumonia and other complications such as systemic inflammatory response syndrome and sepsis. Nowadays procalcitonin (PCT) is the gold standard to differentiate between bacterial and non-bacterial infections in LRTI. The aim of this study was to evaluate if the new Intensive Care Infection Score (ICIS) which is a combination of various cellular measurements made on hematology analyzers could be a potential method to differentiate between bacterial and non-bacterial infections in LRTI. Methods: The ICIS is composed of five blood-cell derived parameters characterizing the early innate immune response; (1) mean fluorescence intensity of mature (segmented) neutrophils; (2) the difference in hemoglobin concentration between newly formed red blood cells and the mature ones; (3) absolute number of segmented neutrophils; (4) absolute count of antibody secreting lymphocytes and (5) absolute count of number of granulocytes. Results: The discriminative power of ICIS to differentiate between patients with LRTI of bacterial and non-bacterial origin is as good or even better as the commonly used infection biomarkers PCT, CRP and IL-6. Conclusions: Beside PCT, CRP and IL-6, ICIS could be used as infection marker in LRTI.