Interpretation
Haemoglobin A1c is an index of metabolic control in patients with diabetes mellitus.
The result correlates best with the mean level of blood glucose during the previous 8 weeks, with the mean blood glucose during the last 30 days prior to testing contributing about 50% of the final result.
HbA1c is formed continuously during the lifespan of the RBC. The HbA1c level depends on (a) the average glucose level , (b) the mean RBC age, and (c) other factors which are not well understood but which are constant for an individuial.
HbA1c measurements may be misleading in cases of haemoglobinopathy, increased red cell turnover or post transfusion. Where there is a suspicion of interference from a haemoglobin variant, further investigation may be undertaken. This may include HbA1c measurement by an alternative method, haemoglobinopathy screen and mass spectrometry. Clinicians should be suspicious when there is discordance between HbA1c and prevailing blood glucose and in that event, should contact the laboratory to discuss.
Reference Intervals
Non-diabetic reference interval 20-40 mmol/mol.
Risk of microvascular complications increases exponentially above 55 mmol/mol.
If >/= 50 mmol/mol and not known to have diabetes, a repeat level >/= 50 after an interval supports the diagnosis.
If result is >65 mmol/mol, consider additional action.
Test Method
Bio-Rad D100, cation exchange HPLC automated testing system.
