Equal health care doesn’t stop anemia from hitting African-American children with chronic kidney disease harder than whites with the same condition, according to study findings published in the American Journal of Kidney Disease and reported in a Johns Hopkins Children’s Center press release.

In general, anemia is a condition in which blood has a lower than normal number of red blood cell or those blood cells don’t have enough hemoglobin. Hemoglobin is an iron-rich protein that makes blood red and helps these cells carry oxygen from the lungs to the rest of the body.

When the hemoglobin level in blood dips below a certain number, this usually means a person is anemic.

For the study, researchers checked the hemoglobin levels of 429 chronic kidney disease patients, ages 1 to 16, at 44 U.S. locations. Scientists found that more black kids had less of the protein in their blood compared with white children.

In addition, researchers found that even with treatment fewer black patients than white ones saw an increase in their hemoglobin levels. And as kidney disease progressed in both groups of kids, the hemoglobin gap increased.

Researchers concluded the findings imply that biological differences—not unequal access to care and treatment—account for why black kids with kidney disease are more seriously threatened by anemia.

“As we move from one-size-fits-all medicine toward individualized medicine, we should study further racial disparities and, perhaps, adjust hemoglobin targets to reflect what appear to be genetic variations,” said Meredith Atkinson, MD, MHS, a pediatric nephrologist at Johns Hopkins Children’s Center in Baltimore, and the study’s lead author.

Scientists also said they’re aware adults with chronic kidney disease exhibit racial differences in hemoglobin levels. And they know that healthy black and white children show slight variations in the protein’s level.

But where doctors must be careful, researchers said, is distinguishing between real anemia and race-related variations in hemoglobin levels.

Read about how diabetes and hypertension can trigger chronic kidney disease in RH’s “The Kidney Punch.”