• In a new study, researchers assessed how ethnicity impacts the success of arteriovenous grafts for dialysis.
• They report that African Americans are more likely to experience graft failure than other ethnicities.
• They also found that the presence of a radiology residency training program in hospitals helps eliminate graft failure risk.
• Further studies are needed to determine why African Americans are more likely to experience graft failure.

Chronic kidney disease (CKD) occurs when the kidneys are damaged and no longer filter blood well.

This can lead to excess fluid and waste remaining in the blood and body. This can increase the risk for health conditions, including heart disease and stroke.

More than 800 million people around the world have CKD and it is one of the leading causes of mortality worldwide. In its final stages, CKD becomes advanced kidney failure (AKF)- when the kidneys no longer meet the body’s needs.

A common treatment option for AKF is hemodialysis, when blood is pumped out of the body and cleaned by an artificial kidney machine before being returned. Physicians commonly use one of three ways to access blood for dialysis:

• Arteriovenous (AV) fistula: a direct connection between an artery and a vein, usually in the arm, via a tube
• Catheter: tubes that are connected to a large vein in the chest or neck for short-term use
• AV graft: an indirect connection between an artery and a vein via a tube or graft typically in the arm

While AV fistulas are the preferred method for dialysis, some people require an AV graft as their veins are too small or weak for a fistula. Studies show, however, that more than half of AV grafts lose function within two years and require maintenance procedures.

More than one maintenance procedure within 30 days increases the risk of death. Previous studies have also found that factors including race, sex, and older age increase the health risks from repeated maintenance.

Recently, researchers investigated how demographic factors such as race may affect AV graft function over time.

They report that African-Americans tend to have a higher risk of impaired AV graft function after dialysis maintenance procedures.

The study was published in the journal Radiology.

How AV graft study was conducted 

For the study, the researchers included 995 people in the United States with an average age of 69 years old who had an AV graft.

Altogether, the patients received 1,950 repeat access maintenance procedures, defined as a hemodialysis access placement occurring 1 to 30 days after an initial procedure.

African-American patients underwent 1,169 (60%) of the 1,950 procedures while people living in the southern United States underwent 1,002, or 51% of procedures. Premature access failure occurred in 215, or 11%, of procedures.

After analyzing the data, the researchers concluded that African American patients were more likely than other races to experience premature access site failure after dialysis maintenance procedures.

They reported that 12% of African Americans underwent access failure while the same was true for 10% of other races.

The researchers found, however, that the presence of a radiology resident training program in hospitals had a protective effect on patients. Race did not affect outcomes among the 1,057 procedures in the 30 facilities with a residency program.

The researchers noted that the average annual income of people who attended centers with residency programs was higher than those without: $48,880 compared to $46,709.

Race and outcome

Medical News Today asked Dr. Mikhail C.S.S. Higgins, an assistant professor of radiology at Boston University and a lead author of the study, what might explain why African American patients were more likely to experience graft failure.

Higgins noted that researchers did not investigate the reasons behind the link in their study and cannot say for certain. He did say there are some potential factors.

“We can presuppose these disparities may stem from systemic inequities in care,” Higgins explained. “These may stem in part from unconscious biases, which as we know from a large body of literature, may be mitigated through intentional awareness, education and shifts in organizational culture.”

Medical News Today also spoke with Dr. J. Wes Ulm, a bioinformatic scientific resource analyst and biomedical data specialist at The National Institutes of Health who was not involved in this study, about the reasons behind the disparity.

Ulm noted that the researchers undertook several measures to rule out discrepancies, such as controlling for common confounding factors, including co-morbid conditions and graft location, and limiting data use from one institution.

“Although conclusions are as yet uncertain, the investigators found indications that, for various reasons, African-American patients may tend to have procedures done at institutions with less experience or honed expertise in AV graft placement, particularly those without interventional radiology resident training programs (a defining feature of a teaching hospital, for example),” he said.

“Such descriptors can be thought of as proxies for underlying factors indicative of operator skill and team experience at graft placement; when the patient pool was limited to those who had received treatment at facilities with such training programs, the observed discrepancy largely disappeared,” Ulm added.

Study conclusions questioned 

MNT also discussed the findings with Dr. Denise Pate, a physician and the medical director for Medical Offices of Manhattan in New York who was not involved in the study.

She noted that the findings do not necessarily mean that African Americans are truly more likely to experience graft failure.

“It is difficult to make this assumption completely in that 12% of the African American population studied had graft failures while 9.6% of the Caucasian population and 11.6% of the Latino population had graft failure and so graft failure is still seen across the board,” Pate said.

“It is known that an AV fistula is superior to AV graft placement in terms of long-term use and patency of the access. African Americans – due to their anatomy with smaller vein diameters – are less successful with AV fistula placement,” she added.

Limitations of the study

Medical News Today also spoke with Dr. Hilary Mull, an associate professor of surgery at Boston University and another of the study’s authors, about the research’s limitations.

She noted that researchers only assessed healthcare data from one healthcare institution, so they cannot generalize their findings to other systems.

“There are also clinical and socioeconomic factors potentially associated with outcomes that we could not capture. Our study provides an important first step in identifying a problem for further investigation, however, and future work should examine causal factors associated with these disparities,” she added.

Takeaways from the AV graft study

Higgins noted that there are two major takeaways from the findings.

The first is that African American patients have a higher risk of dialysis access dysfunction and failure than other races.

The second, he noted, is that residency programs are linked to previously unstudied environmental factors that can protect Black patients from worse outcomes.

Pate added that something to further investigate is how to intervene and prevent AKD so that vascular access becomes a non-issue.

“This occurs with access to care for all ethnicities and recognizing the difference in surveillance between ethnicities. It may be necessary to evaluate kidney function through a different lens when working with African American patients,” she concluded.

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