Fewer Children, More Blacks Hospitalized for HUS in US, 2007-18

But trends study finds bulk of hospital stays in patients ages 10 or younger

Marisa Wexler, MS avatar

by Marisa Wexler, MS |

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The demographics of people hospitalized for hemolytic uremic syndrome (HUS) in the U.S. have shifted over the last decade, with a lower proportion of young children and a higher number of Black patients, a new study reports.

“Further surveillance is required to determine if these trends continue,” the researchers wrote.

The study also suggests that older age and a need for dialysis are risk factors for in-hospital mortality in HUS-related hospitalizations.

The study, “Trends and Outcomes of Hospitalizations Due to Hemolytic Uremic Syndrome: A National Perspective,” was published in the journal Cureus.

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HUS is a condition where blood vessels become inflamed and damaged, causing injury to the kidneys. The typical form is caused by a bacterial infection, whereas in atypical HUS (aHUS) there is usually a genetic mutation that predisposes individuals to having altered immune activity.

Researchers analyzed data from a large U.S. database called the Nationwide Inpatient Sample (NIS) to assess trends in HUS-related hospitalizations from 2007 to 2018.

“Our study did not differentiate between typical versus atypical HUS since the genetic [testing needed to identify aHUS] is not routinely performed,” the team wrote.

Over the decade studied, more than 8,000 HUS-related hospitalizations were documented. The median length of a HUS-related hospital stay was eight days. Just over half (53.5%) of the hospitalizations were paid for by private insurance, and most of the remaining ones (38.1%) were paid for by public insurance programs funded by the U.S. government (Medicare/Medicaid).

There were 528 hospitalizations in 2007, and the yearly rate of hospitalizations increased steadily in the following years, reaching a peak of 800 in 2013. The rate then decreased over the next few years, with 620 HUS-related hospitalizations in 2018.

Most of the patients who were hospitalized over the decade studied were children ages 10 or younger. Yet, the proportion of young patients who were hospitalized decreased steadily — from 63.8% in 2007 to 46.77% in 2018.

Most of the recorded hospitalizations were for whites, though the proportion of white patients fell steadily from 73.08% in 2007 to 67.83% in 2018. The proportion of Hispanic patients similarly declined, from 15.55% in 2007 to 6.09% in 2018, whereas the proportion of Black patients increased from 4.19% to 19.13%.

“Our study also showed that in Black patients, the hospitalization trend is steadily increasing, while it is declining in other populations,” the researchers wrote. They also noted that “the reasons are unclear,” and called for further studies to investigate.

The proportion of hospitalized HUS patients with acute kidney injury increased from 54.82% in 2007 to 77.42% in 2018, while the number of patients requiring dialysis at any time rose from 28.29% to 36.29%.

Among all of the recorded hospitalizations, the rate of in-hospital mortality was 3.03%, and 15.69% of patients were sent from the hospital to receive further care at a specialized nursing facility (SNF), which implies that their disease was not well enough controlled for them to be sent home. Researchers conducted a battery of statistical tests to look for factors associated with these adverse outcomes.

Results showed that older patients were at a higher risk of in-hospital mortality or discharge to an SNF. The risk of in-hospital mortality was more than two times higher in patients who required dialysis, compared with those who never needed it.

Patients with co-occurring health problems, like diabetes or heart disease, were more likely to be sent to a SNF. Hospital-level factors, like bed size and hospital type, also were associated with SNF discharge.

“There were several demographic and patient-level and hospital-level characteristics associated with in-hospital mortality and discharge to SNFs,” the researchers wrote.

The team noted that this study was limited only to in-hospital outcomes, which don’t always directly line up with long-term outcomes.