RESUMEN
Background: Proteinuria has been commonly reported in patients with COVID-19, suggesting a renal involvement in this infection. However, only dipstick tests have been used thus far. Here, the quantification and characterization of proteinuria and hematuria are investigated. Their potential association with mortality was assessed. Methods: This retrospective, observational and monocentric study includes 153 patients hospitalized with COVID-19 between March 28th and April 30th 2020, in whom total proteinuria and urine α1-microglobulin (a marker of tubular injury) have been measured. Association with mortality was evaluated with a follow-up until May 7th 2020. Results: According to the Kidney Disease Improving Global Outcomes staging, 14% (n=21) had stage 1 proteinuria (<150 mg/g of urine creatinine), 42% (n=64) had stage 2 (between 150 and 500 mg/g) and 44% (n=68) had stage 3 (over 500 mg/g). Urine α1-microglobulin concentration was higher than 10 or 15 mg/g in 94% and 89% of patients, respectively. After a median follow-up of 27 [14;30] days, the mortality rate reached 18%. Total proteinuria and urine α1-microglobulin (as continuous and/or categorical variables) were associated with mortality in unadjusted and adjusted models. This association was even stronger in subgroups of patients with normal renal function or without urinary catheter. Conclusions: Proteinuria is frequent in patients with COVID-19. Its characterization suggests a tubular origin with increased urine α1-microglobulin. Tubular proteinuria seems associated with mortality in COVID-19.