Type 2 diabetes is being misdiagnosed in African Americans

Wellcome researchers have found that the standard test for type 2 diabetes may not be accurately diagnosing the disease in African Americans.

The nurse deposits a drop of patient's blood on the strip of the glucometer

Credit: Belmonte / Science Photo Library

The standard test for type 2 diabetes measures the amount of glucose carried by the red blood cells.

The standard test for type 2 diabetes is known as the glycated haemoglobin or HbA1c test. It measures the amount of glucose that is carried by the red blood cells over the previous two to three months.

The team found that a genetic variant carried almost exclusively by African Americans significantly reduced the accuracy of the test. At least one copy of the variant in the G6PD gene is carried by around 11 per cent of African Americans.

This could mean that up to 650,000 African Americans in the USA could have undiagnosed type 2 diabetes if tested with only HbAc1.

Dr Eleanor Wheeler, joint first author from the Wellcome Trust Sanger Institute, said: "The G6PD genetic variant shortens the three-month lifecycle of red blood cells. So in African Americans who have this variant, their red blood cells don’t live long enough to bind to the glucose in the blood. Therefore these people will have a lower level of HbA1c, which won’t show as a positive result for type 2 diabetes."

The results suggest that screening for type 2 diabetes could include both the HbA1c test and a test for the G6PD variant in populations with African ancestry.

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