Use of HbA1c in the diagnosis of diabetes mellitus in the UK. The implementation of World Health Organization guidance 2011.

The WHO was very clear that an HbA(1c) of 48 mmol/mol (6.5%) and above is diagnostic of diabetes. They were less clear regarding results that fell below 48 mmol/mol. The WHO recognize that individuals with HbA(1c) values below the cut-off point may still have diabetes, but give no guidance on how to investigate further. It is important that these individuals, who may be at increased risk of developing diabetes, are monitored correctly; a recommended scheme is given in Fig. 2; following these recommendations will ensure at-risk people are not overlooked and will be monitored closely. Even although it is not recommended to combine HbA(1c) with glucose measurement for diagnosis, the WHO did not discount the value of a fasting glucose and an oral glucose tolerance test to diagnose diabetes in selected individuals; it is the responsibility of the investigating doctor to choose how best to diagnose on an individual basis. This new method of diagnosing diabetes will identify a different cohort as having diabetes than is currently being diagnosed; but the process of investigation that does not require a fasting sample makes investigation easier, allowing more people to be investigated.