Int J Lab Hematol. 2020;00:1–5. wileyonlinelibrary.com/journal/ijlh | 1 © 2020 John Wiley & Sons Ltd 1 | INTRODUCTION Assessment of organ failure and mortality risk in critically ill patients is possible through Systemic Organ Failure Assessment (SOFA) and APACHE II scores. According to the results of prospective studies, 1-3 higher SOFA score is associated with increased mortality. APACHE II score is based on 17 physical and laboratory parameters as well as from data on personal history. 4,5 Received: 4 June 2020 | Revised: 16 June 2020 | Accepted: 15 July 2020 DOI: 10.1111/ijlh.13308 ORIGINAL ARTICLE Improvement of mortality prediction accuracy in critically ill patients through combination of SOFA and APACHE II score with markers of stress haematopoiesis Michaela Macichová 1 | Monika Grochová 2 | Oliver Rácz 3 | Jozef Firment 2 | Miriam Mitníková 1 | Jaroslav Rosenberger 4 | Jana Šimonová 2 | Vladimir Hudák 2 1 Clinical Hematology Unit, Department of Laboratory Medicine, Louis Pasteur University Hospital, Košice, Slovakia 2 1st Department of Anesthesiology and Intensive Medicine, Medical School, Louis Pasteur University Hospital, Šafárik University, Košice, Slovakia 3 Medical School, Institute of Pathological Physiology, Šafárik University, Košice, Slovakia 4 Nephrological and Dialysis Centre Fresenius, Košice, Slovakia Correspondence Oliver Rácz, Medical School, Institute of Pathological Physiology, Šafárik University, Košice, Slovakia. Email: olliracz@gmail.com Abstract Introduction: In critically ill patients nucleated red blood cells (NRBC) and immature granulocytes (IG) appear in the peripheral blood as the consequence of stress hae- matopoesis. The aim of this retrospective study was to evaluate the diagnostic value of NRBC and IG and to propose a model of improved mortality prediction including these parameters in the assessment of critically ill patients. Methods: The study included 338 critically ill adult patients hospitalized at Department of Anaesthesiology and Intensive Medicine, Louis Pasteur University Hospital in Kosice. As NRBC positive patients were considered patients with periph- eral NRBC > 0.01 × 10 9 /L and IG positivity as >0.03 × 10 9 /L. Apache II index was calculated 24 hours after admission and Systemic Organ Failure Assessment (SOFA) on the day with the worst clinical condition. Results: NRBC positivity was found in 27.6% of patients. The mortality of NRBC posi- tive patients was 48.38%, significantly higher than 23.7% of NRBC negative patients. IG positivity was 79.0% and their mortality was also higher as compared with that of IG negative patients (69.3% vs 33.8%). Three regression models predicting mortality including stress haematopoiesis markers, APACHE II, SOFA scores and age had suf- ficient level of sensitivity and specificity. Conclusion: The presence of NRBC in the peripheral blood and the IG increase are available early risk predictors of mortality in critically ill patients. Regression models designed by combination of SOFA, APACHE II, and the new haematological param- eters increase the accuracy and effectivity of diagnostic process in predicting prog- nosis and risk of mortality with high sensitivity and specificity. KEYWORDS critical conditions, haematopoiesis, immature granulocytes, nucleated red blood cells