DISCUSSION
Children of all ages, regardless of gender, can be infected with COVID-19 infection, although more cases have been reported in younger children and infants (9). Furthermore, the mean age of infection in children up to age of 15 was determined as 6.7 (9). In their study, Lara S et al found the rate of boys as 52% and the median age as 13 (4.2-16.6) years (10). Again, in a recent study, boys 13 (65%), Girl 7 (35%), Age <1 month 3 (15%), 1 month-1 year 6 (30%), 1-3y 5 (25%) (11). In this study, the rate of boys in PCR (-) covid-19 cases was found as 44.9%, while the rate of boys in PCR (+) cases was determined as 50.8%. addition, the age distribution was 13% 0-1 years, 15.2% 2-3 years, 134-6 years, 20%, 3-10 years and 38.4% 11-18 years. In the light of the data discussed above, it is possible to say that there is no difference in terms of age or gender in COVID-19 cases (9). Currently, it is difficult to define the clinical characteristics of children with COVID-19 infection since there are small number of scientific clinical studies conducted on children (12). In a study conducted in China, the rate of asymptomatic COVID-19 infection in children was reported as 13% (13). In a previous study conducted in different countries, while the most common clinical symptoms in children with covid-19 were determined as Cough (%21-85.1), Fever (%26-59.2), Shortness of breath (%2.67-59.2), Diarrhea 1 (%3.7-7.6), jess frequently sore throat, sneezing, fatigue and vomiting have been reported (3,4,11,14,16). Also it has been reported that children may have more upper respiratory symptoms than lower respiratory symptoms and recover within 1-2 weeks (9,17). In this study, the most common clinical symptoms in children were determined as fever (64.7%), cough (53.2%), respiratory distress (12.2%), myalgia (24.5%) and diarrhea (12.9%). In addition, diarrhea and cough symptoms were more common in younger age group children, while myalgia was significantly more common in older age group children. It can be concluded that the use of these clinical findings in the diagnosis of COVID-19 is limited since clinical symptoms are nonspecific in children, they are observed at low rates and may be confused with many upper respiratory tract infections. COVID-19 infection can affect many laboratory parameters in children (3). In a study conducted in Italy, 36.8% and 15.7% leukopenia and lymphopenia were detected among the patients, respectively, while AST and ALT increases were reported as 18.3% and 11.8%, respectively (3). Henry et al., In their study conducted on 66 children, determined normal leukocyte counts (69.2%), neutropenia (6.0%), neutrophilia (4.6%), lymphopenia (3.0%), high C-reactive protein (13.6%) and high procalcitonin (10.6%). 20 children were evaluated in a study published in China, it was determined that leukopenia (20%), lococytosis (10%), lymphopenia (35%), lymphocytosis (15%), high ALT (25%), high creatine kinase-MB as (75%) (11). In this study, it was determined that high CRP (35.3%), ALT (5.8%), high AST (11.5%), high WBC as (23.7%) and low WBC as (14.4%), while high level of ALT, AST, WBC, Lymphocyte were determined as statistically significantly higher in younger age group children and high neutrophilia in older age group. In the light of given data, it is possible to say that laboratory parameters are important parameters in the diagnosis and follow-up of COVID-19. Some recent studies have reported that CT imaging, especially in adults, may have a high sensitivity and prognostic value (5). However, since the severity and frequency of COVID-19 pneumonia is observed lower in pediatric patients in comparison with adults, the imaging findings, mode of involvement and the role of CT imaging may differ from adult patients (6,7). In a study conducted in Italy, it was reported that 41.5% of children with chest X-ray had ground glass opacity and 9.8% had focal consolidation (3). In another study, it was reported that there was 29.33% no abnormality in CT imaging, 29.3% local patch shading, 34.6% bilateral patched shading, and 6.67% ground glass opacity (3). In another study, it was reported that there was 20% normal, 30% unilateral and 50% bilateral involvement on chest CT (11), in another, CT findings that reminded the infection were found in 25.9% of pediatric patients (19), in this last study, the presence of lung Rx findings (48.2%) and CT findings (24.5%) were detected in the patients. It is understood that lung CT imaging is a very limited test in diagnosis and follow-up, since COVID-19 infection in pediatric cases is generally less common and milder in comparison with adults. The standard test for the diagnosis of COVID-19 is considered as the RT-PCR test, especially in patients without obvious clinical findings (5). While PCR test positivity makes the diagnosis of COVID-19 with full accuracy, PCR test negativity may be seriously insufficient to determine the diagnosis of COVID-19. The major reason for this is the high false negativity of the PCR test due to many factors, especially in children and adult COVID-19 patients without obvious clinical findings (5). Specifically, in the largest study from China, most cases were diagnosed as an outpatient and only 34.1% of cases were confirmed by the laboratory (20). At the time of diagnosis, 13-15% of virologically positive children may be asymptomatic (13,15). While in this study, the PCR positivity rate was determined as 43.9%, the frequency of fever, high CRP, leukocytosis, high neutrophil and CT findings were detected statistically significantly higher in PCR (-) cases compared to PCR (+) cases, frequency of respiratory distress, high lymphocyte and CT findings were significantly lower. Within the scope of given data, it is understood that when the PCR test is used for diagnostic purposes in children, it is a test with low sensitivity and it may cause false-negative, especially in cases with fever, high CRP, leukocytosis, high neutrophil and respiratory distress in CT findings.
As a result, COVID-19 infection may indicate different nonspecific clinical, laboratory and radiological findings in children not only compared to adults but also among pediatric age groups. In addition, PCR test results are being affected by conditions like fever, respiratory distress, high CRP, leukocytosis, high neutrophil and CT finding. We believe that further comprehensive studies are needed on this subject.