Incidence of new-onset proteinuria in AKI associated with COVID-19 is not greater than it is in AKI from other causes

Background: Early reports of acute kidney injury (AKI) associated with COVID-19 have claimed high incidence of proteinuria If so, it may suggest an AKI pathogenesis not solely related to ischemic acute tubular injury (ATI) We hypothesized that those claims result from observation bias Therefore, we sought to investigate the rate of De novo proteinuria in AKI associated with COVID-19 (CoV-AKI) compared to that of AKI in the pre-COVID-19 era (non-CoV-AKI) Methods: Hospitalized patients with CoV-AKI entered the cohort (n=161) As a control non-CoV-AKI group (n=186), we accessed a database of patients with AKI who underwent urinary sediment microscopy due to suspicion of an intrinsic cause of AKI (Sedi-AKI cohort, 2017-2019) We examined the incidence of proteinuria of any degree (1+ dipstick), significant [urine protein-to-creatinine ratio (UPCR) ≥ 0 5-3 0 g/g or 2+ dipstick] or overt [UPCR ≥ 3 0 g/g + 3+ dipstick] Results: Median age were similar: 65 (34-95) and 60 (20-88) years for CoV-AKI and non-CoV-AKI, respectively Women were 62% and 63% (p=0 86) Black race was more common in CoV-AKI (75% vs 35%;p=<0 0001) ATI (ischemic and/or toxic) was the presumed cause of AKI in 75% and 71% of CoV-AKI and non-CoV-AKI, respectively Incidence of any, significant or overt proteinuria were 123/148 (83%) vs 127/184 (69%) (p=0 003), 98/148 (66%) vs 81/184 (44%) (p=0 0001) and 14/148 (10%) vs 23/184 (13%) (p=0 39), for CoV-AKI and non-CoV-AKI, respectively Among those with significant proteinuria, no difference in median UPCR was found [0 69 vs 0 69 g/g (p=0 23)] Using baseline UPCR when available, rates of De novo significant and overt proteinuria were similar [57/124 (46%) vs 57/123 (46%) (p=1 00) and 6/124 (5%) vs 7/123 (7%) (p=0 75)] Among overt cases who underwent kidney biopsy, collapsing glomerulopathy was found in 3/4 (75%) in the CoV-AKI group compared to 0/11 (0%) in the control (p=0 002) Conclusions: The incidence rate of new onset proteinuria was not found to be increased in CoV-AKI and is consistent with that of other forms of ATI An observed overall greater incidence in significant proteinuria in CoV-AKI may be driven by preexisting proteinuria While the rate of overt proteinuria is not greater in CoV-AKI, the primary cause of De novo glomerular disease may vary