Genetic variant in South Asians affects diabetes test accuracy

A genetic variant found predominantly in people with South Asian ancestry has been shown to affect the accuracy of a commonly-used type 2 diabetes test.

HbA1c tests indicate the average blood glucose levels over two to three months by measuring the amount of sugar attached to red blood cells, and are one of the tests a doctor will use to decide if a person has diabetes or prediabetes. According to research presented at the Diabetes UK Professional Conference, in people who carry the genetic variant, HbA1c test results can be misleadingly low, potentially resulting in missed diagnosis and treatment.

'Many genetic variants linked to red blood cell conditions are ultra-rare amongst the Northern Europeans who have historically dominated genetic studies,' said study leader Dr Miriam Samuel, NIHR academic clinical fellow at Queen Mary University London. 'We demonstrate one such variant that is carried by 7.6 percent of South Asians which could affect the accuracy of HbA1c and cause delays in diabetes diagnosis.'

The team analysed data from Genes and Health, which involves approximately 50,000 British Bangladeshi and Pakistani volunteers, and from the UK Biobank, including 500,000 individuals of varied ethnicity living in the UK. The findings suggest that the genetic variant leads to changes in red blood cells, which affect the HbA1c test results. The researchers found that individuals carrying this variant were diagnosed with type 2 diabetes on average one to two years later than those without it.

'This evidence showing that the accuracy of a common test to diagnose and monitor type 2 diabetes is linked to a person's ethnicity should be urgently investigated further', Dr Elizabeth Robertson, director of research at Diabetes UK, London, told the Independent. 'It's incredibly important that healthcare professionals are armed with a precise way to evaluate average blood sugar levels over extended periods. Without this, they are navigating in the dark and potentially at risk of overlooking cases of type 2 diabetes.'

People with Bangladeshi, Indian and Pakistani ancestry represent 6.9 percent of the English and Welsh population. Approximately 7.6 percent of South Asians carry this variant, suggesting that thousands of diabetes and prediabetes cases might have been missed.

'Studies such as Genes and 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', said Dr Samuel.

Alternative blood sugar tests, such as fasting glucose and oral glucose tolerance tests, could be used by doctors when evaluating whether people with this genetic variant have diabetes or prediabetes.