Staph Bloodstream Infections in Hemodialysis: Access Type, Race, Ethnicity and Poverty

End-stage kidney disease falls hardest on racial and ethnic minorities, and patients on hemodialysis are at high risk of Staphylococcus aureus (staph) bloodstream infections. This CDC Vital Signs report, posted as an MMWR Early Release on February 6, 2023, looked at how those infections relate to race, ethnicity and social conditions.

In short: the type of vascular access was the biggest risk factor, with central venous catheters the worst — but race, ethnicity and socioeconomic factors also shaped who got infected, and Hispanic ethnicity was an independent risk factor.

Background

More than 800,000 Americans live with end-stage kidney disease; 70% are treated with dialysis (89% of them hemodialysis, 11% peritoneal dialysis) and 30% have a working transplant. It is four times as common among Black people and more than twice as common among Hispanic people as among White people — partly because of high blood pressure and diabetes — and these groups, along with people with lower income or poorer insurance, also get less kidney care before dialysis and fewer treatment options. Black people are 33% of U.S. dialysis patients but 12% of the population.

Infections are a leading cause of illness and death on hemodialysis, and staph is the germ most often found in their bloodstream infections; 40% of those are methicillin-resistant (MRSA). Risk is highest with catheters, lower with grafts and lowest with fistulas.

The data

• National Healthcare Safety Network (NHSN), 2020: infections reported by dialysis facilities, linked to county social-vulnerability data.
• Emerging Infections Program (EIP), 2017–2020: population-based surveillance of adult hemodialysis patients in selected counties at seven sites, with patients' race, ethnicity and census tract.

Findings

Nationally, 2020. 4,840 facilities reported 14,822 bloodstream infections; 34.2% were staph (about half methicillin-sensitive and 37.9% MRSA). Compared with a fistula, a catheter carried about six times the risk (adjusted rate ratio 6.2) and a graft or other access about twice. Facilities affiliated with a hospital, not part of a chain, without a written antibiotic-use policy, or in areas with more older adults also had somewhat higher rates.

EIP areas, 2017–2020. Of 2,800 staph bloodstream infections, the rate among hemodialysis patients was 4,248 per 100,000 person-years, against 42 among other adults — 100 times higher.

• Infections were concentrated in poorer, more crowded, less educated census tracts: 42.1% occurred in the tracts with the most poverty against 10.4% in those with the least, though the population was spread about evenly across the quartiles.
• Unadjusted rates were highest among Black and Hispanic patients, men, younger patients, catheter users and some sites; the highest of all was among Black patients aged 18–49, 65% of whose infections involved catheters.

• After adjustment, Hispanic ethnicity (40% higher risk than White patients), male sex, younger age (18–49, adjusted rate ratio 1.7 against 65 and over) and some sites were independent risk factors — but catheter access had the strongest effect of all. Black patients' risk was not significantly higher once access type, age, sex and site were accounted for.
• Hispanic patients actually used catheters less (13.9%) than White (23.1%) or Black (20.8%) patients, so catheters alone do not explain their higher risk. How long catheters stay in may matter: one study found Black patients 65 and older spent about 40 more days on catheters than White patients, and Hispanic patients and those of other races 20 to 30 more. Education about catheter care and the resources available for it may play a part.

What the authors recommend

Hemodialysis bloodstream infections have fallen since 2014 thanks to staff and patient education, catheter-care practices, audits and surveillance, but staph remains a major problem. The authors call for a comprehensive approach: better prevention and management of diabetes and high blood pressure; earlier diagnosis and treatment of chronic kidney disease; better access to the best treatments for end-stage disease, especially in poorer areas; culturally and linguistically appropriate education on access care and infection prevention, particularly for Hispanic patients; research into why and for how long catheters are used, and removing barriers to lower-risk access; and best-practice infection prevention for every patient. Linking surveillance data more closely — patient-level access type, race, ethnicity and socioeconomic status, ideally reported automatically — would sharpen the picture.

Limits

The national facility data were linked to county-level social-vulnerability data that were not patient-specific, so some facility associations are hard to interpret; and the EIP data could not give infection rates by socioeconomic factors, only counts by tract quartile. The two systems also find cases differently.

Sources

• Rha B, See I, Dunham L, et al. "Vital Signs: Health Disparities in Hemodialysis-Associated Staphylococcus aureus Bloodstream Infections — United States, 2017–2020." MMWR, CDC, 2023. https://www.cdc.gov/mmwr/volumes/72/wr/mm7206e1.htm
• The public summary: CDC Vital Signs — Preventing Bloodstream Infections in People on Dialysis.
• Figures: CDC.
• Rewritten in hubnx's own words.