Proteinuria in COVID-19: prevalence, characterization and prognostic role

J Nephrol. 2021 Apr;34(2):355-364. doi: 10.1007/s40620-020-00931-w. Epub 2021 Jan 23.


Background: Proteinuria has been commonly reported in patients with COVID-19. However, only dipstick tests have been frequently used thus far. Here, the quantification and characterization of proteinuria were investigated and their association with mortality was assessed.

Methods: This retrospective, observational, single center study included 153 patients, hospitalized with COVID-19 between March 28th and April 30th, 2020, in whom total proteinuria and urinary α1-microglobulin (a marker of tubular injury) were 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) of the patients had category 1 proteinuria (< 150 mg/g of urine creatinine), 42% (n = 64) had category 2 (between 150 and 500 mg/g) and 44% (n = 68) had category 3 proteinuria (over 500 mg/g). Urine α1-microglobulin concentration was higher than 15 mg/g in 89% of patients. After a median follow-up of 27 [14;30] days, the mortality rate reached 18%. Total proteinuria and urinary α1-microglobulin were associated with mortality in unadjusted and adjusted models. This association was stronger in subgroups of patients with normal renal function and without a urinary catheter.

Conclusions: Proteinuria is frequent in patients with COVID-19. Its characterization suggests a tubular origin, with increased urinary α1-microglobulin. Tubular proteinuria was associated with mortality in COVID-19 in our restropective, observational study.

Keywords: COVID-19; Proteinuria; Tubular proteinuria; α1-microglobulin.

Publication types

  • Observational Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aged
  • Aged, 80 and over
  • Belgium / epidemiology
  • Biomarkers / urine
  • COVID-19 / complications*
  • COVID-19 / epidemiology
  • COVID-19 / urine
  • Female
  • Humans
  • Male
  • Middle Aged
  • Prevalence
  • Prognosis
  • Proteinuria / epidemiology*
  • Proteinuria / etiology
  • Proteinuria / urine
  • Retrospective Studies
  • Survival Rate / trends


  • Biomarkers