A new global study led by a team from the University of Queensland has found that millions of COVID patients may have undiagnosed acute kidney injury, prompting researchers to call for a more comprehensive definition of AKI to be implemented as soon as possible.
AKI is one of the most common and significant problems associated with COVID infection, with existing data indicating that some 20% of patients admitted to hospital with COVID develop AKI, rising to roughly 40% for those in intensive care.
It is traditionally identified using the Kidney Disease Improving Global Outcomes (KDIGO) definition, which relies on the rise of creatinine levels in the blood (sCr), either by 26.5 μmol/l in 48 hours or by 50% from baseline over a 7-day period.
Yet by using a modified definition proposed by the International Society of Nephrology, which accounts for a fall in the level of sCr early in admission, the researchers found that the rate of AKI diagnosis in COVID patients nearly doubled.
UQ PhD candidate and kidney specialist Dr Marina Wainstein explained that while KDIGO can capture AKI that develops during a hospital stay, it may fail to identify cases that have developed in the community and are potentially recovering by the time a patient presents to the hospital, thereby underestimating the true incidence of AKI.
“That was a pretty shocking finding,” Dr Wainstein said.
“If that creatinine rise occurs before a patient presents to hospital, we can miss the AKI diagnosis and fail to manage the patient appropriately in those early, critical days of hospitalisation.
“Even though the AKI is already starting to improve in hospital, our research shows that these patients have worse in-hospital outcomes and are more likely to die compared to patients with no AKI.”
To address this potential limitation of the KDIGO definition, the ISN added a commensurate fall in sCr to their definition of AKI, making it a more comprehensive and inclusive definition.
And to test it, the researchers collected data from 418,111 people admitted to hospital with COVID, from 1,609 sites across 54 countries.
Of the 75,670 people used as the final analysis cohort, 12,704 (16.8%) patients were identified as having AKI during their admission using the KDIGO definition – using the extended KDIGO definition, a total of 23,892 (31.6%) patients were diagnosed with AKI.
Peak sCr occurred more frequently on days 3 and 6 from admission and diminished significantly after day 10 using a KDIGO definition. With the extended definition, an additional 4,019 patients had AKI on day 3 (70% of all AKI diagnosed on that day) and 1,808 on day 6 (64% of all AKI on that day).
Study supervisor Dr Sally Shrapnel, from UQ’s School of Mathematics and Physics, said the findings are particularly relevant for populations from resource-poor countries, where community acquired AKI is also more common.
“These people have limited access to healthcare and are more likely to present late in the disease process,” Dr Shrapnel said.
“Now we have the data showing a large gap in AKI diagnosis exists, it’s time to test this definition in a clinical trial so we can identify all AKI patients early and hopefully prevent these awful outcomes.”