HbA1c screening for undiagnosed diabetes in New Zealand

To describe a screening programme to detect undiagnosed diabetes in high-risk ethnic groups in New Zealand and determine the specificity and sensitivity of HbA(1c) to detect fasting hyperglycaemia.

HbA(1c) was offered to subjects over 20 years of age participating in a screening programme for hepatitis B that was targeted at non-European populations. Two hundred and forty-four predominantly Maori subjects, with HbA(1c) levels 5 to 7.9% and who were not known to have diabetes, were tested with an oral glucose tolerance test. Comparison was made with fasting and 2-h samples.

Fifty thousand eight hundred and nineteen subjects were screened using HbA(1c). 12% had HbA(1c) levels of 6.1% or more, and in 4% of the population HbA(1c) was 7.1% or more. Maori, Pacific Island people, and Indians had particularly high rates of elevated HbA(1c). HbA(1c) levels of 6.1% and greater were 94% sensitive and 77% specific in detecting the 32 subjects who had a fasting glucose of 7.0 mmol/L or more, and 90% sensitive and 73% specific for 20 subjects with a 2-h glucose of 11.1 mmol/L or more.

Rates of elevated HbA(1c) levels in non-Europeans in New Zealand are very high, particularly in Maori, Pacific Island Peoples', and Indians, reflecting their high risk of diabetes and vascular disease. HbA(1c) can be used as an opportunistic screening test for diabetes and glucose intolerance, but a high level should be followed by an oral glucose tolerance test.