T2d test and South Asians

New research has identified a genetic variant amongst people of South Asian heritage that may give falsely lower results for HbA1c tests.

Using genetic and health data from the Genes & Health study (over 60,000 individuals of Bangladeshi or Pakistani ethnicity living in England) and the UK Biobank (500,000 people of varied ethnicity living in the UK),

Dr Miriam Samuel at Queen Mary University London and colleagues in the Genes & Health Research Team identified a genetic variant that is found in 7.6% of people of South Asian heritage, but is ‘ultra rare’ in other ethnicities.

Individuals with this variant were found to have falsely lower HbA1c levels and differences in their full blood count. The research suggests that the genetic variant is linked to changes in red blood cells, and that this affects HbA1c test results. For those with two copies of the genetic variant (homozygous), HbA1c test results could be falsely lower by around 6 mmol/mol.

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 and are therefore at high risk of developing Type 2 diabetes. With around 7.6% of South Asians carrying this variant, this suggests that the HbA1c test is underestimating blood sugar levels in around 32,000 South Asian people with diabetes and 17,500 with pre-diabetes in England alone.

The findings indicate that additional blood sugar testing, such as fasting glucose and oral glucose tolerance tests, and alternative monitoring pathways might be needed in South Asian people who carry the variant. The researchers also emphasise the importance of ethnic diversity in genetic research and recommend that further research is needed to explore whether inaccurate HbA1c results are contributing to the diabetes inequalities experienced by South Asian people living in the UK.

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