Type 2 diabetes is being misdiagnosed in African-Americans, genetic study suggests

September 12, 2017, Wellcome Trust Sanger Institute
Credit: CC0 Public Domain

One of the tests used to diagnose type 2 diabetes and monitor blood sugar control is influenced by 60 genetic variants, an international team of scientists, including those from the Wellcome Trust Sanger Institute, has found. One genetic variant in particular, found only in African Americans, significantly reduces the accuracy of the HbA1c blood test used to diagnose and monitor the condition. This means around 650,000 African Americans in the US could have undiagnosed type 2 diabetes if tested with the HbA1c test alone.

The results, published today (12 September) in PLOS Medicine suggest screening for the particular genetic alongside the diagnostic , or using other in populations with African ancestry in order to improve diagnoses of type 2 diabetes.

There are over 4 million people living with diabetes in the UK, and this number is estimated to rise to 5 million by 2025. Ninety per cent of these cases are type 2 diabetes, which is associated withincreasing rates of obesity. In the US, the number of people with diabetes is more than 29 million.

In the largest study of its kind, an international team of more than 200 scientists investigated genetic variants which are thought to affect the blood test used to diagnose and monitor type 2 diabetes, known as the glycated haemoglobin, or HbA1c test.

The team studied genetic variants in almost 160,000 people from European, African, East Asian and South Asian ancestries who were not known to have type 2 diabetes. Researchers discovered 60 genetic variants that influence the outcome of HbA1c tests, of which 42 variants were new.

One genetic variant in particular, in the G6PD gene, was found to significantly impact the results of the HbA1c test. The G6PD genetic variant is almost unique to people of African ancestry; around 11 per cent of African Americans carry at least one copy of this variant.

Dr Inês Barroso, joint lead author from the Wellcome Trust Sanger Institute, said: "The issue with the G6PD genetic variant is it artificially lowers the value of blood sugar in the HbA1c test, and can lead to under-diagnosis of people with type 2 diabetes. We estimate that if we tested all Americans for diabetes using the HbA1c test, we would miss type 2 diabetes in around 650,000 African Americans. However, the HbA1c test remains a suitable test for diagnosing and monitoring diabetes for the majority of people."

The HbA1c test measures the amount of glucose, or sugar that is carried by the red blood cells in the body, for the previous two to three months.

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 don't live long enough to bind to the glucose in the . Therefore these people will have a lower level of HbA1c, which won't show as a positive result for type 2 diabetes."

Dr James Meigs, joint lead author from Massachusetts General Hospital and Harvard Medical School, said: "We now need further studies involving people of diverse ancestries to assess how diagnostic tests for diabetes should be altered to account for . In the meantime, an option would be to genetically screen African Americans for the G6PD variant alongside the HbA1c test in order to accurately diagnose type 2 diabetes, or use other diagnostic tests such as fasting glucose measurements. We suggest moving towards precision medicine to take people's genetics into account and improve diagnosis and monitoring for ."

Explore further: Children at risk of diabetes should be screened by HbA1C, oral glucose tolerance tests

More information: Eleanor Wheeler et al. (2017) Impact of common genetic determinants of Hemoglobin A1c on type 2 diabetes risk and diagnosis in ancestrally diverse populations: A transethnic genome-wide meta-analysis. PLOS Medicine. DOI: 10.1371/journal.pmed.1002383

Related Stories

Children at risk of diabetes should be screened by HbA1C, oral glucose tolerance tests

April 4, 2017
Doctors should add an oral glucose tolerance test (OGTT) to their hemoglobin A1C (HbA1C) when they screen high-risk children for prediabetes and diabetes, new research from South Korea suggests. The study results will be ...

Sickle cell trait may confound blood sugar readings among African-Americans

February 7, 2017
A new study in JAMA provides evidence that hemoglobin A1c (HbA1c), a common blood biomarker used to measure blood sugar over time, may not perform as accurately among African-Americans with sickle cell trait and could be ...

Continuous subcutaneous insulin infusion bests injections in T2DM

April 7, 2017
(HealthDay)—For patients with type 2 diabetes and hemoglobin A1c (HbA1c) >8 percent following multiple daily injections (MDI), continuous subcutaneous insulin infusion (CSII) is associated with a significantly greater reduction ...

Fasting plasma glucose, HbA1c linked to alzheimer's in T2DM

July 25, 2017
(HealthDay)—For patients with type 2 diabetes mellitus (T2DM), fasting plasma glucose (FPG) visit-to-visit variation, represented by the coefficient of variation (CV), and hemoglobin A1c (HbA1c) CV are independently associated ...

Combining tests leads to better prediabetes detection

November 30, 2015
Using a combination of two blood sugar tests rather than a single test would improve detection of prediabetes in American children and adults, according to a new study by researchers at the School of Public Health at Georgia ...

African-Americans respond better to first-line diabetes drug than whites

June 12, 2014
African Americans taking the diabetes drug metformin saw greater improvements in their blood sugar control than white individuals who were prescribed the same medication, according to a new study published in the Endocrine ...

Recommended for you

Bariatric surgery successes lead to type 2 diabetes treatment

April 24, 2018
Bariatric surgery has long yielded almost immediate health benefits for patients with type 2 diabetes, and new findings on the reasons for remission may be the key to developing drug alternatives to surgery.

Hacking human 'drug trafficking' network could make diabetes treatments more effective

April 23, 2018
Making tiny changes to existing diabetes treatments can alter how they interact with cells, and potentially make the medicines more effective.

Vitamin D deficiency linked to greater risk of diabetes

April 19, 2018
An epidemiological study conducted by researchers at University of California San Diego School of Medicine and Seoul National University suggests that persons deficient in vitamin D may be at much greater risk of developing ...

One class of drug used to treat type 2 diabetes may not reduce the risk of death when compared with placebo

April 17, 2018
One class of drug used to treat type 2 diabetes may not reduce the risk of death when compared with placebo, suggests new findings.

People with Type 2 diabetes who eat breakfast later, more likely to have a higher BMI

April 16, 2018
Being an "evening person" is linked to higher body mass indices among people with Type 2 diabetes, and having breakfast later in the day seems to be what drives this association, according to a new paper in the journal Diabetic ...

Continuous glucose monitors proven cost-effective, add to quality of life for diabetics

April 12, 2018
Continuous glucose monitors (CGM) offer significant, daily benefits to people with type 1 diabetes, providing near-real time measurements of blood sugar levels, but they can be expensive. A new study by researchers from the ...

2 comments

Adjust slider to filter visible comments by rank

Display comments: newest first

omegatalon
not rated yet Sep 12, 2017
If these individuals do not have Type II Diabetes then what is the cause of the high glucose levels in the individuals blood.
johnp
not rated yet Sep 12, 2017
As it says in, IIRC, paragraph 9 of the article, in those with the G6PD genetic variant the test under reports the amount of glucose because their red blood cells don't live long enough for the glucose to sufficiently bind to the cells thus leading to a false negative.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.