Evaluation of KL-6 and sRAGE as Alveolar Damage Markers in Pediatric COVID-19 Cases: Is sRAGE the Key Reason for Clinical Differences in Pediatric and Adult COVID-19 Patients?

Objective: KL-6 and sRAGE, produced by pneumocytes, are novel biomarkers for pulmonary diseases. These markers were found to be elevated in COVID-19 adult patients. The aim of this study was to identify a possible inflammatory biomarker for COVID-19 in children and evaluate these biomarkers to predict clinical course. Methods: Between 01.01.2021 and 31.12.2021, 61 patients (mild and moderate) and 27 control participants aged from 1 month to 18 years were included in the study, and a nonrandomized prospective case-control study was designed. KL-6 and sRAGE levels were evaluated in all participants and compared between each group. Results: The mean age of study group was 148 +/- 56 months, and 51.1% were girls. There was a statistically significant difference in the median of sRAGE and KL-6 of the groups. sRAGE was statistically significant lower in moderate group than uninfected group, KL-6 was statistically significant higher in moderate group than uninfected and mild groups. In identifying moderate patients, cut-off values of >= 180.3 and >= 3.08 were determined for KL-6 and sRAGE with sensitivity of 71% and 73.3% and specificity of 66.7% and 77.2%, respectively. ROC analysis of KL-6 and sRAGE distinguished COVID-19 patients from healthy subjects, with an area under curve of 0.71 and 0.29, respectively. Conclusion: In conclusion, this study showed that serum KL-6 concentrations were elevated in children with moderate COVID-19, which correlated with the severity of the disease. Furthermore, the low level of sRAGE in moderate patients may help explain the difference between pediatric and adult COVID-19 course.