Evaluating Tubulopathy and Podocytopathy in COVID-19 Patients with Proteinuria Using Urinary NGAL and Podocalyxin Levels

Background: Clinical observations have shown that renal dysfunction is frequently seen in hospitalized COVID-19 patients. The mechanisms and pathways of kidney involvement in COVID-19 patients are not yet fully understood. Podocalyxin is an anionic transmembrane protein localized on the apical surface of glomerular podocytes. Podocalyxinuria indicates glomerular level damage to podocytes and/or the presence of apoptotic and necrotic podocytes in the urine. NGAL protein is freely filtered by the glomeruli and mostly reabsorbed by the proximal tubules. NGAL expression is rapidly induced in response to renal tubular epithelial cell damage and inflammation, and it is thought to be a marker of both acute and chronic kidney damage. Methods: Our study includes patients with proteinuria and hypoalbuminemia who were hospitalized and followed up with a diagnosis of COVID-19 at Gazi University Faculty of Medicine Hospital (n=72) and a control group (n=48). Urinary podocalyxin and NGAL levels were measured in these patients. Results: Podocalyxin and NGAL levels were significantly higher in proteinuric patients. NGAL levels were significantly associated with COVID-19 severity and disease mortality.(both p value <0.05= Correlation analysis of podocalyxin showed significantly higher levels in patients with proteinuria greater than 1000 mg/day. Conclusion: Current literature does not provide studies showing whether the kidney damage seen in COVID-19 patients with proteinuria, hematuria, and GFR loss is due to direct viral damage to the kidney glomeruli and podocytes or related to the septic and hemodynamic condition. Therefore, assessing the impact on glomeruli and predicting patient and renal prognosis non-invasively without kidney biopsy by measuring urinary podocalyxin and NGAL in COVID-19 patients with proteinuria, hematuria, and renal dysfunction will be possible. This study is the first to investigate the presence of podocyturia in COVID-19 patients. Funding: Private Foundation Support