Research led by Dr Miriam Samuel and colleagues in Genes & Health shows that a gene variant almost exclusively found in people of South Asian heritage affects the accuracy of the HbA1c test commonly used to diagnose type 2 diabetes.
In this study, funded by Diabetes UK, Dr Samuel and her colleagues used genetic and health data from the Genes & Health study of over 60,000 individuals of Bangladeshi or Pakistani ethnicity living in England, and the UK Biobank of 500,000 people of varied ethnicity living in the UK, to identify a genetic variant that is found in 7.6% of people of South Asian heritage but which is extremely rare in other ethnicities. When given the HbA1c test – which measures average blood sugar levels over the preceding two to three months - the gene caused a falsely low result.
The research team further analysed health records of South Asian people carrying this genetic variant and compared them to records of people without it. They found that individuals with one copy of the gene had their diabetes diagnosed on average one year later than others, while people with two copies of the gene had their diagnoses delayed by two years, on average. These delays can have serious consequences, as without timely and appropriate treatments to manage blood sugar levels people may have greater risk of long-term complications, including heart attacks, strokes, amputations, and sight loss.
In England, it is estimated that there are over 420,000 people from a South Asian background living with diabetes, and over 230,000 have a diagnosis of prediabetes. With around 7.6% of South Asians carrying this variant, the research suggests that the HbA1c test is underestimating blood sugar levels in around 32,000 South Asian people with diabetes and 17,500 with prediabetes in England alone. Alternative types of blood sugar testing, such as fasting glucose tests, and additional monitoring pathways for people with this genetic variant, may be needed to ensure diagnoses are not delayed.
Dr Miriam Samuel, NIHR Academic Clinical Fellow in the Primary Care Unit, Wolfson Institute of Population Health, said: “Many genetic variants linked to red blood cell conditions are ultra-rare amongst the Northern Europeans who have historically dominated genetic studies. We demonstrate one such variant that is carried by 7.6% of South Asians which could affect the accuracy of HbA1c and cause delays in diabetes diagnosis. Studies such as Genes & Health, focusing on populations who are underserved in genetic research, are vital to understand the different pathways that may contribute to diabetes inequalities in these communities.”
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