African Americans with sickle cell trait – a condition in which a person does not have sickle cell disease but has one copy of its associated gene – may be at higher risk of chronic kidney disease than those without the condition. This is according to a study published in JAMA.

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Researchers found that African Americans with sickle cell trait had higher rates of chronic kidney disease than those without the condition.

Sickle cell trait (SCT), or sicklemia, affects around 1-3 million people in the US and 8-10% of African Americans. It is an inherited condition in which an individual carries a single copy of the gene that causes sickle cell disease – a group of inherited red blood cell disorders – but people with SCT never develop the disease.

In very rare cases, a person with SCT may have blood in their urine. Severe dehydration or high-intensity activity may also cause people with the condition to develop deformed red blood cells, but this is also extremely rare.

According to the research team, including Dr. Rakhi P. Naik of Johns Hopkins University in Baltimore, MD, some people with sickle cell disease develop renal conditions, such as chronic kidney disease (CKD) and end-stage renal disease (ESRD).

They note, however, that it has not been established whether individuals with SCT – particularly African Americans – are at higher risk of such conditions.

“African Americans have a disproportionately higher risk of CKD and progression to ESRD, compared with white or Asian-American populations,” the researchers note. “SCT may be an important and unrecognized risk factor for renal disease in this population.”

To find out, Dr. Naik and colleagues analyzed five US population-based studies involving 15,975 African Americans. Of these, 1,248 had SCT.

The team identified CKD among 2,233 participants. Of these, 19.2% of cases occurred among individuals with SCT, while 13.5% of cases were among those without the condition.

The rate of incident CKD was also higher among individuals with SCT than those without the condition, at 20.7% and 13.7%, respectively.

The researchers also found that people with SCT had a faster decline in estimated glomerular filtration rate (eGFR) – the rate at which fluid is filtered through the kidney; 22.6% of those with sickle cell trait experienced eGFR decline, compared with 19% of those without the condition.

What is more, 31.8% of people with SCT experienced albuminuria – excess protein in urine that can be a sign of a kidney disorder – compared with 19% of those free of SCT.

Commenting on their findings, the researchers say:

In this large multicohort study, SCT was associated with CKD and incident CKD, decline in eGFR, and albuminuria in African Americans.

These associations […] may offer an additional genetic explanation for the increased risk of CKD observed among African Americans, compared with other racial groups.”

The team says their findings also highlight the need for more research into the renal complications that may be associated with SCT. “Because screening for SCT is already being widely performed, accurate characterization of disease associations with SCT is critical to inform policy and treatment recommendations,” they add.

Medical News Today recently reported on a study suggesting that following a Mediterranean-style diet could reduce the risk of chronic kidney disease.