A retrospective study of age-defined hematologic inflammatory markers related to pediatric COVID-19 diagnosis.

Background: The aim of this study was to examine age-related differences in hemogram parameters and hematologic inflammatory markers in pediatric patients with COVID-19.

Methods: This retrospective study included children aged 2 months to 18 years (n = 208) who have a confirmed diagnosis of COVID-19 and a control group comprising 117 healthy children between February 2021 and July 2021. The analysis of subgroup hematological values were performed according to the children's age cutoffs.

Results: The most significant difference between pediatric patients with COVID-19 and controls were peripheral blood eosinophil counts and eosinophil-to-monocyte ratio (EMR) levels on admission. The levels of monocyte-to-lymphocyte ratio, aggeregate index of systemic inflammation (neutrophil × platelet × monocyte/lymphocyte), neutrophil-to- lymphocyte × platelet ratio, and systemic inflammation response index (neutrophil × monocyte/ lymphocyte) were higher in patients than in controls. EMR had the highest area under the curve (AUC) value of 0.777, with a cutoff value of 0.26. The sensitivity for EMR was 75% under 2 years of age, and between 78.6-87.5% in the other age groups.

Conclusion: In children younger than 6 months, the discriminative power of hematological indices is low, while the discriminative power of EMR is high at all ages when age appropriate cutoffs are used. Hematological inflammatory parameters may be particularly practical in pediatric clinics to help identify COVID-19 infection.