A test used to monitor long-term blood sugar levels in diabetes patients may give deceptively high results for children with an African background, researchers say. The misleading results could lead to incorrect treatment and potentially life-threatening complications.

What do we know already?
If someone has diabetes, they have too much sugar in their blood, in the form of glucose. Treatment aims to keep blood glucose within normal levels.

A blood test can tell you your blood glucose level at any one time, but doctors also test for a chemical called HbA1c. HbA1c responds to blood glucose levels, so an HbA1c test gives doctors an idea of what your blood glucose has been over time – like an average over the previous two or three months. Doctors typically recommend that people with diabetes have an HbA1c test at least once a year, to see if their diabetes is under control.

Researchers have been looking at the factors that can influence someone’s HbA1c results, to make sure that test results are used accurately to decide on treatment. In a new study, researchers looked at whether someone’s ethnic group had an effect on their test results.

What does the new study say?
The researchers compared the HbA1c results of African-American children with those of white children. African-American children tended to have higher HbA1c scores, even when their average blood glucose levels were similar. This suggests that HbA1c results might need interpreting differently for African-Americans.

The researchers looked at 276 children from a New Orleans hospital. They all had type 1 diabetes, which tends to start while someone is in their teens. After adjusting for other factors that could have influenced the test results, including recorded blood glucose scores, the average HbA1c for African-American children was 9.1 percent (76 mmol/mol), compared with 8.3 percent (67 mmol/mol) for white children.

Where does the study come from?
The study appeared in a journal called Diabetes Care, published by the American Diabetes Association.

What does this mean for me?
Type 1 diabetes is treated with insulin injections. These work by stopping a person’s blood sugar levels getting too high, but if treatment is too aggressive, blood sugar levels can get dangerously low.

Low blood sugar is called hypoglycaemia. Someone with hypoglycaemia will feel weak, drowsy, and confused. Most people learn to handle mild hypoglycaemia themselves, by eating or drinking something sugary. But severe hypoglycaemia can lead to seizures or unconsciousness, and even be life-threatening without prompt treatment.

While ordinary blood glucose tests would give the correct results for black children, the new research suggests that an HbA1c test would be misleadingly high, perhaps leading doctors to think that treatment isn’t working as well as it should. This could lead to more aggressive treatment that reduces someone’s blood sugar too much, and leads to episodes of hypoglycaemia.

According to Dr Stuart Chalew, a paediatrician at the New Orleans School of Medicine, “If doctors don’t take both HbA1c and self-monitored blood sugar levels into account, they are likely to unintentionally provoke increased episodes of life-threatening hypoglycaemia in African-American patients”.

Black people tend to have a higher risk of getting complications from diabetes, which could partly be explained by their HbA1c levels responding differently to their blood sugar. In the long term, this finding may lead to new treatments to prevent diabetes complications.

We don’t know how well results from African-American children in the US translate to black children from African or African-Caribbean backgrounds in the UK. There hasn’t been research in the UK to look at this.

What should I do now?
The researchers recommend that doctors are especially careful to look at average blood glucose levels, as well as HbA1c, when treating black children with type 1 diabetes.

If you’re concerned about your treatment for diabetes, or you find yourself getting episodes of low blood sugar, talk to your doctor. He or she can help you re-evaluate your treatment.

From:
Kamps JL, Hempe JM, Chalew SA. Racial disparity in A1c independent of mean blood glucose in children with type 1 diabetes. Diabetes Care. 2010; 33: 1025-1027.

BMJ Publishing Group Limited (“BMJ Group”) 2010