Haemoglobin A1c (HbA1c) encompasses integrated value of blood glucose fluctuations over a period of 3 months and has been employed as a standard monitoring system for diabetes control by health care professionals.
Many clinical trials (eg DCCT) have shown its efficacy in depicting long-term complications of diabetes and its good correlation with average blood glucose levels.
This test principle involves non-enzymatic glycosylation (i.e. irreversible bonding of glucose to proteins) of haemoglobin in red blood cells (with a life span of 90-120 days), the rate of reaction being proportional to the levels of ambient blood glucose levels.
Glucose diffuses freely into RBC and attaches to specific moiety of haemoglobin (Hb) forming a specific sub-fraction (HbA1c) which is measured by various methods.
It doesn’t require fasting state, has greater precision and pre-analytic stability and thus offers more convenience to the patients and doctors.
On the downside, it suffers from its inability to account for acute blood glucose changes, being expensive and limited use in special conditions like:
- hemoglobinopathies
- pregnancy
- aging
- chronic kidney disease.
It has been used in the diagnosis and subsequent follow-up of diabetic patients successfully.
| HbA1c* values | Interpretation |
|---|---|
| ≤5.6% | Normal |
| 5.7-6.4% | Pre-Diabetes |
| ≥6.5% | Diabetes |
*measured by High performance liquid chromatography certified to conform to NGSP standard
