NEW YORK – Researchers from the ASSESS-AKI acute kidney injury study have found that patients' urinary albumin-creatinine ratio (ACR) is predictive of kidney disease progression.
The findings, published on Monday in JAMA Internal Medicine, could help doctors better manage patients who develop AKI during a hospital stay and assess their risk of developing further kidney problems, said Chi-yuan Hsu, chief of nephrology at the University of California, San Francisco and first author on the study.
Hospital-induced AKI is a relatively common phenomenon with many estimates putting the incidence rate at around 2 percent of hospitalized adults. It has a variety of causes, including conditions like sepsis and procedures including surgery and imaging using contrast media.
Despite the high incidence, or perhaps because of it, follow up of hospital-induced AKI is often inconsistent, with little in the way of clear guidelines, Hsu said.
"A lot of doctors see it, but they don't pay that much attention," he said. "So you might have AKI in the hospital and then you might go back to your primary care doctor and they don't really know that it happened."
Research, including work by clinicians at New York's Northwell Health hospital system, also suggests that hospital-induced AKI is significantly underreported. In a pilot program run by the hospital system using lab data to better identify patient's suffering from AKI, the system found that more careful monitoring of patient creatinine results boosted documented AKI cases from around 6 to 7 percent to 12 to 14 percent.
Hsu added that some studies have shown that occurrences of AKI are in many cases not mentioned in patients' discharge summaries.
Typically, he said, patients receive no additional care or monitoring after the occurrence of AKI during hospitalization.
"There's no recommendation guideline," he said. "And the current rate of monitoring of things like ACR [in these patients] is extremely low. We really don't know how to risk-stratify people after AKI, what is the appropriate follow up, what is the appropriate medical therapy."
Awareness of this potential gap in patient care is growing, though, Hsu said. He cited a workshop held last year sponsored by the National Institute of Diabetes and Digestive and Kidney Diseases that tried to define appropriate follow-up after AKI.
"They were trying to bring attention to this problem and also highlight the gaps in the literature," he said.
The ASSESS-AKI (Assessment, Serial Evaluation, and Subsequent Sequelae of Acute Kidney Injury) study was launched in 2009 to better understand how hospital-induced AKI impacted patient risk of developing chronic kidney disease as well as other outcomes like cardiovascular events and death. The study enrolled 1,538 hospitalized adults — half of whom developed AKI during their hospital stay and half of whom did not — at four North American hospitals between 2009 and 2015.
As part of the study, patients had their ACR measured at three months after being discharged from the hospital, which allowed Hsu and his colleagues to investigate whether that score might be useful for predicting who was likely to experience worsening kidney disease.
"This was not one of the primary aims of the study, but we took advantage of the data structure to study this question," he said.
The researchers found that higher post-AKI urine ACR scores were linked to an increased risk of developing kidney disease and that this association was stronger in patients who experienced hospital-induced AKI than those who did not.
The results suggest that an ACR check at three months after discharge could help doctors triage patients who require specialist attention, Hsu said, noting that another problem presented by the high incidence of hospital-induced AKI is that the number of cases would overwhelm the available nephrologists.
"Most people who have AKI of mild to moderate severity, not requiring dialysis, will not be seen by nephrologists," he said. "Just like internists check for albumin in urine in patients with diabetes and if they have albumin in their urine then they send them to the kidney specialist, [internists] should do the same thing [with AKI patients]. It's a simple test and they should do it for screening purposes."
Hsu said that while the usefulness for measuring ACR to assess kidney disease risk has been established in other populations like patients with diabetes, the JAMA Internal Medicine study was the first to demonstrate its utility in AKI patients.
"I think it is reliable, solid evidence based on a research cohort," he said, adding that while "all research needs to be replicated," the fact that ACR has been shown to be useful for assessing risk of kidney disease in other settings gives him confidence to the results will hold up.
Hsu said that doctors have not typically checked ACR in patients post-AKI because "up to this point, there has been no data showing that it is useful. I think that our study establishes that it is useful and important, and so we conclude that people should check it."
The ASSESS-AKI study did not find that AKI or severity of AKI were linked to more rapid progression of kidney disease independent of urine ACR, estimated glomerular filtration rate, demographics, and other traditional kidney disease risk factors.
Hsu said this was likely because the occurrence of AKI was reflected in those measures.
Those measures assess "the mechanisms by which AKI accelerates kidney disease progression," he said. "We're not saying that AKI is benign. What we are saying is that AKI's 'badness,' so to speak, is largely captured by what happens to the state of the patient after AKI."