Access Point Choice, Sociodemographic Factors Affect S Aureus Risk in Hemodialysis

Demographic and socioeconomic factors are already known to affect a patient’s risk of end-stage kidney disease (ESKD), but a new report suggests these factors can also convey a higher risk of infection when patients receive hemodialysis to treat the disease.

The data, from the Centers for Disease Control and Prevention’s (CDC) Morbidity and Mortality Weekly Report, suggests Hispanic ethnicity, lower education levels, and higher poverty were all associated with an increased risk of Staphylococcus aureus (S aureus) bloodstream infections.

Previous data have shown that Black Americans are more than 4 times as likely to be diagnosed with ESKD compared to White Americans, and Hispanics have double the risk, noted corresponding author Shannon Novosad, MD, of the CDC’s National Center for Emerging and Zoonotic Infectious Diseases, and colleagues. However, the investigators added that there are also disparities in access and quality of care, including pre-dialysis care, which may be one reason Black patients make up 33% of the patients receiving dialysis in the United States, even though they make up just 12% of the population.

Those receiving dialysis are at a higher risk than patients not receiving dialysis of S aureus infection, an infection that is often methicillin resistant. However, not all instances of dialysis carry the same risk level, they noted.

“Type of hemodialysis access is a well-established risk factor for infections; risk is highest for central venous catheters (CVCs), lower for grafts, and lowest for fistulas,” Novosad and colleagues said.

Given the demographic disparities already observed in ESKD risk and dialysis use, the investigators wanted to see whether demographic factors were also associated with the risk of S. aureus infections.

Novosad and colleagues analyzed data from 2 sources: the 2020 National Healthcare Safety Network (NHSN) surveillance database, and the CDC’s Emerging Infections Program (EIP).

In the NHSN data set, 14,822 bloodstream infections were reported at a total of 4840 dialysis facilities. About one third of those bloodstream infections—34.2%–were said to be caused by S aureus.

In the EIP data set, which included the years 2017-2020 and was based on 7 sites, the investigators found the risk of S aureus bloodstream infection was 100 times higher among people on hemodialysis compared to those not on hemodialysis.

As expected, the access point used for dialysis played a significant role in the risk of S aureus infection. In the NHSN database the adjusted risk ratio (aRR) for infection using CVC versus fistula as the access point was 6.2 (95% confidence interval [CI], 5.7-6.7); in the EIP database the aRR for infection using CVC versus fistula or graft was 4.3 (95% CI, 3.9-4.8).

In order to look at demographic factors, the investigators adjusted the EIP data set for residence, sex, and vascular access type. After doing so, they found that Hispanic patients had the highest risk of S aureus infection compared to White patients (aRR of 1.4; 95% CI, 1.2-1.7 and 1.7). They also found patients ages 18-49 had a higher risk of infection than those aged 65 and older (aRR 1.7; 95% CI, 1.5-1.9).

Higher poverty, crowding, and lower education levels disproportionately increased a person’s risk of S. aureus infection, they found.

Though Hispanic patients were at a significantly higher risk of infection compared to White patients, the same was not true for Black patients, after adjustment.

“[W]hereas higher crude rates were observed in Black patients in the current study, race was not a statistically significant factor in multivariable analyses, suggesting the higher unadjusted rate might be mediated by other factors; in contrast, Hispanic ethnicity was independently associated with a 40% higher risk for S aureus bloodstream infection,” Novosad and colleagues said.

The investigators said the relationships between age, race, ethnicity, social determinants of health, and hemodialysis-associated infection are complex and worthy of additional study. They said the current study was constrained by limits on the type of data available in the two data sets.

They also said more research is needed to better understand when and why CVC access is used in hemodialysis, despite the higher infection risk.

In the meantime, the authors said dialysis centers may help improve patient outcomes with better patient education, including cultural- and language-appropriate education programs.

“Regardless, education and implementation of established best practices to prevent bloodstream infections are critical to protecting the entire hemodialysis patient community, including those most at risk,” they concluded.