Methods
Children admitted to the Emergency Department of Ministry of Health Ankara City Hospital Children’s Hospital, which is a tertiary children hospital with 555 beds capacity, with symptoms including fever, sore throat, rhinorrhea, cough between 1-15 April 2020, were included in the study. All patients were tested for SARS-CoV-2 by quantitative real-time reverse transcription polymerase chain reaction from combined nasal and oropharyngeal swab samples. Complete blood count test and peripheral smear were done on admission of Emergency Department. Patients unable to obtain peripheral blood smear were excluded from the study. Thirty children were tested to be positive for SARS-CoV-2 and the remaining 40 symptomatic children were tested to be negative.
Complete blood count (CBC) was analyzed with Siemens ADVIA 2120i Hematology Analyzer with Auto slide (Siemens Healthcare Diagnostics, Erlangen, Germany); CBC results, including differential count results, were noted. Estimated absolute lymphocyte (ALC), neutrophil (ANC), monocyte (AMC) counts, were recorded from CBC results and were also calculated from peripheral smear specimens. Hemoglobin, leukocyte and neutrophil values were assessed according to age-specific intervals (16); ALC<3x109/L and ALC <1.5x109/L were accepted as lymphopenia in <12-month and >12-month old patients, respectively (16). Neutropenia was diagnosed with an absolute neutrophil count of <1.5x109/L (16). Neutrophil/lymphocyte ratio was calculated by the ADVIA 2120i analyzer. C-reactive protein values were also recorded.
All patients’ peripheral blood smear specimens (May-Grünwald-Giemsa stain x100) were evaluated for neutrophil, thrombocyte and erythrocyte morphology and differential counts were formulated by manual counting including reactive lymphocyte and immature myeloid cells (band, metamyelocyte and myelocyte). the peripheral smears was blindly evaluated to the SARS-CoV-2 test result. The correlation between the reactive lymphocyte count in manual peripheral smear and large unstained cells (LUC), which reflects the activated lymphocytes and peroxidase-negative cells as measured by ADVIA 2120i, was analyzed. Moreover, the correlation between the percentage of immature myeloid cells in peripheral smear and delta neutrophil index (DNI) was assessed; DNI reflects immature myeloid cells and is calculated by subtracting polymorphonuclear leukocyte count in nuclear lobularity channel from neutrophil and eosinophil count in myeloperoxidase channel, both measured by the ADVIA 2120i analyzer.
The data were expressed as mean ±SD. Student’s t-test was used to compare the means. Pearson correlation was used to assess the relationship between two quantitative, continuous variables. A value of p<0.05 was considered significant.