Time stability of Intensive Care Infection Score (ICIS) as a cellular hematology biomarker for infection in critically ill patients

The Intensive Care Infection Score (ICIS) is composed of blood-cell derived parameters to discriminate infection or sepsis from non-infectious inflammatory responses. The study examines the stability of the complete blood count (CBC) and ICIS after blood sample storage at room temperature (RT) and determines the impact of potential variations on ICIS and its clinical interpretation. In total, 53 K3-EDTA-blood samples collected from critically ill patients were analyzed at baseline (t0) and after 8 h (t1) on a hematology analyzer. After a mean storage time of 514 min at RT, all ICIS parameters in the CBC are stable. Observed transitions of ICIS classification were neither statistically (p = 0.082) nor clinically relevant as no sample was classified as falsely positive or falsely negative. This study demonstrates the stability of the ICIS in K3-EDTA whole blood for up to 8 h at RT, preserving its clinical interpretation and utility in distinguishing infection from non-infectious inflammatory responses, even if analysis is delayed.