Researchers say that different cut-off values for different age groups may be needed if the UK switches to HbA1c testing to diagnose type 2 diabetes, after their study questioned its accuracy for determining the diabetic status of older patients.
Ninety Asian patients aged an average of 60.3 years and with no prior diabetes underwent an HbA1c test and an oral glucose tolerance test. They were divided into four age groups – 50 years or younger, 50-59 years, 59-72 years, and 72 years or older.
Using a cut-off of 6.2% cut-point became less accurate with age. The sensitivity and specificity decreased from 88.9% and 72.7% in the youngest group to 54.5% and 66.7% in the oldest group.
But using an HbA1c cut-point of 6.5% in the 72 years and older group reduced the false positives and negatives to 8.8% and 23.3%, respectively.
Lead researcher Dr Tay Tunn Lin, an endocrinology fellow at Changi General Hospital, Singapore said: ‘HbA1c used in isolation from OGTT may not be sufficient to confidently diagnose Type 2 diabetes mellitus in this group and different cut-off values for different age groups may be a more appropriate solution.’
Diabetes Res Clin Pract 2011, online Feb 1
HbA1c testing inaccurate for older patients