Acute Kidney Injury With COVID-19 Seems to Be Declining in US

Jenny Blair

December 17, 2020

Editor's note: Find the latest COVID-19 news and guidance in Medscape's Coronavirus Resource Center.

Among US veterans hospitalized with COVID-19, about one third experienced acute kidney injury (AKI) during the pandemic's first wave, but there was a marked downward trend in AKI from the spring to the summer, and this was mainly due to shifts in the racial makeup of the patient population, say the authors of the new national cohort study.

"We observed quite a big difference in the rates of AKI across Veterans Affairs hospital systems, ranging from 10% to 56%," said coauthor Miao Cai, PhD, a statistician with the Veterans Affairs St Louis Health Care System, Missouri. Cai made the comments in a podcast that accompanies their article, which was published online in the Clinical Journal of the American Society of Nephrology, with lead author Benjamin Bowe, MD, from the same institution.

"But perhaps as a silver lining, AKI rates declined by about a third, from 40% in March to 27% in July," Cai adds. "In both instances, variability in AKI rates were strongly associated with the percentage of population being treated that was black."

While previous reports of COVID-associated AKI have used regional data, this observational cohort study sheds light, for the first time, on the phenomenon at a national level.

And nephrologist Anitha Vijayan, MD, of the Washington University School of Medicine in St Louis, Missouri, who was not involved with the current study, has recently observed a big decline in AKI in patients with COVID-19 during the second wave of the pandemic at her institution, compared with the first wave.

"Is anyone else seeing less COVID-19—associated AKI now, despite rising COVID-19 hospitalizations and ICU admissions?" she recently tweeted.

She suggested to Medscape Medical News that, in her region at least, race-based differences in presentations with COVID-19, over time, could be related to masking policies.

"At least for Missouri, what has happened is that the St Louis city and county [have] a mask mandate, and now most of our patients who are coming to the hospital with COVID-19 are from the outlying counties, because the governor doesn't have a mask mandate," Vijayan said. "Those [patients] tend to be White, in the rural areas."

Other factors that could account for the temporal shift in AKI rates among patients hospitalized with COVID-19 include a rising proportion of younger patients with fewer comorbidities and an increased emphasis on noninvasive positive pressure ventilation over intubation, Vijayan suggested.

"What's happening in the kidney [with COVID-19] is not a direct viral involvement in most patients. It's basically [that] we're seeing acute tubular injury that we would see in any patient with critical illness," Vijayan said.

"Mechanical ventilation does play a role in maybe avoiding that might prevent renal injury."

A Veterans' COVID-19 Cohort: Many Left Hospital With Unresolved AKI

In their report, Bowe and colleagues analyzed the electronic health records of 5216 patients of the US Department of Veterans Affairs health system, excluding those with end-stage kidney disease or no record of an outpatient baseline serum creatinine in the previous 7 to 365 days.

All had been hospitalized with a positive COVID-19 test between February 1 and July 23. Follow-up proceeded through July 30.

Of that group, they identified those who developed AKI during or after hospitalization. Primary outcomes were all-cause mortality, discharge, and need for mechanical ventilation.

AKI occurred in 1655 patients (32%), of whom 201 (12%) required renal replacement therapy. Most developed the injury within the first day of hospitalization. Upon discharge, creatinine was higher than baseline in 47%.

"This may suggest that a large number of patients are coming into the hospital already with kidney injury," said coauthor Ziyad Al-Aly, MD, also of the Washington University School of Medicine, in the podcast.

"A large number of patients left the hospital with unresolved AKI. These patients may need long-term care and could suffer long-term consequences."

AKI was associated with worse outcomes, including higher mortality and ventilator use and longer hospital stays.

On adjusted multivariable analysis, predictors of both AKI and of more severe AKI included Black race, age, male gender, obesity, type 2 diabetes, and hypertension. The risk of AKI-associated death was higher among Black patients compared with Whites.

Black Race Largely Explains Hospital-Level and Temporal Variability

Marked differences in AKI incidence occurred by geography and time. In both cases, Black race largely accounted for the variability.

Hospital-level rates varied from 10% to 56%. Black race accounted for about 31% of differences in hospital systems' AKI rates, with higher rates in systems that care for more African Americans.

Other factors accounting for geographic difference included mean age (11%); mean Area Deprivation Index (ADI), a measure of socioeconomic disadvantage (10%); obesity rates (9%); diabetes rates (9%); hypertension rates (9%); and chronic kidney disease rates (9%).

In addition, over time, AKI rates among the cohort steeply declined.

In March, 40% of the hospitalized cohort developed AKI; in July, it was 27%. Black race accounted for 49% of that temporal variability, with smaller percentages related to diabetes (10%), mean age (7%), hypertension rates (6%), obesity rates (1%), and ADI (1%).

Severity of kidney injury also declined among those with AKI, with 17% in stage 3 or requiring renal replacement therapy in July, compared with 44% in March. 

Epidemiology Likely to Keep Shifting

Study limitations included a lack of data on AKI etiology or individual socioeconomic status. And generalizability from the VA's population, which comprises predominantly older white men, is unclear.

"As the pandemic continues to rage unabated in the United States, characteristics of people infected with COVID-19 will likely continue to change," the authors write.

"Further shifts in the epidemiology of COVID-19–associated AKI are to be anticipated."

The study was funded by the US Department of Veterans Affairs; the Institute for Public Health at Washington University in St Louis Missouri; and two American Society of Nephrology and KidneyCure predoctoral fellowship awards. The authors have reported no relevant financial relationships.

Clin J Am Soc Nephrol. Published online November 16, 2020. Full text

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