Haemoglobin A1c (HbA1c)

Normal Reference Range

HbA1c (DCCT-aligned)

<6.4%

HbA1c (IFCC Reference)

<46 mmol/mol

Test Information

Glycosylated haemoglobin, often known as HbA1c, is a kind of haemoglobin that is typically evaluated to determine the average plasma glucose concentration over time. It is created through a non-enzymatic glycation route that involves plasma glucose exposure of haemoglobin. Over the course of the red blood cell's lifespan, which is typically 120 days, hemoglobin is glycosylated at a variable (non-linear) rate. This indicates that the average glucose level over the previous 120 days determines the proportional proportion of glycosylated haemoglobin at any one period.

Clinical Indications

Monitoring of Diabetes. However, it has limited utility in the diagnosis of diabetes mellitus.

Note: Where the average RBC lifespan is much less than 120 days, the HbA1c assay is not recommended since up to 50% of glycosylation normally takes place between days 90 and 120. Situations that frequently rule out HbA1c assays include: -

1. Red cell disorders with increased red cell turnover, including anaemia, myelodysplastic disease, haemolysis, and hemoglobinopathies

2. Interferences include carbamylated haemoglobin (in patients with uraemia), persisting foetal haemoglobin, and haemoglobin variations.

Very poorly controlled diabetics: HbA1c readings will be correspondingly misleading in patients who habitually vary between very high and very low plasma glucose levels.

Sample Required

4mL EDTA Whole blood tube is required for the HB A1C blood test

Min. sample volume

0.5mL

Special Instructions and Precautions

None

Time Limits For Retrospective Testing

5 days

Any factors affecting the test

None

Turnaround Time

3 days

Referral centre (if applicable)

Not applicable

Test Code

A1C