Platelet Count and Platelet Indices as Predictive Markers of COVID-19 Mortality

The aim of the study was to analyze changes in platelet count and function in hospitalized COVID-19 patients and compare them with non-COVID-19 patients, focusing on the association between platelet indices and mortality beyond the known link between neutrophil-to-lymphocyte ratio (NLR) and COVID-19 severity. The study sample consisted of 572 patients, out of which 472 were hospitalized with COVID-19 infection from 15th October 2021 to 30th April 2022 in Louis Pasteur University Hospital Kosice, Slovak Republic and 100 represented the control group without COVID-19 infection. COVID-19 positive patients (n=472) had significantly larger size of platelets (MPV 9.2+/-1.4 vs. 8.8+/-1.2, p=0.002) and therefore a higher percentage of platelets larger than 12 fl (P-LCR 33.7 % vs. 24.8 %, p=0.002) than patients in the control group (non-COVID19). The statistically significant relationship was between mortality in patients with COVID-19 infection (n=122) and the larger size of the platelets (MPV), higher platelet large cell ratio, (P-LCR), higher PLT/MPV ratio, higher platelet distribution width to plateletcrit ratio (PDW/PCT), higher neutrophil-to-lymphocyte ratio (NLR) (p<0.001, respectively) and lower platelet count (PLT) and lower plateletcrit (PCT) (p=0.006; p=0.028; respectively). In multivariable logistic regression analysis, a significant positive correlation between mortality, MPV (OR 2.29; 95 % CI 1.70-3.08, p<0.001) and age (OR 1.06; 1.03-1.08, p<0.001) was observed. When NLR was included into this model, MPV was stronger predictor of mortality (OR 2.48; 95 % CI 1.79-3.43, p<0.001) compared to NLR (OR 1.06; 95 % CI 1.03-1.08, p<0.001) and age (OR 1.04; 95 % CI 1.02-1.07, p<0.001). MPV is a strong and independent predictor of mortality in hospitalized COVID-19 patients, demonstrating superior prognostic value compared to established association between neutrophil-to-lymphocyte ratio (NLR) and COVID-19 severity. As a simple and routinely available parameter from standard blood count, MPV may serve as a practical and accessible tool for early risk stratification in the clinical management of COVID-19. Key words Platelets " COVID-19 " Mean platelet volume " Neutrophil to lymphocyte ratio " Mortality.