Special Precautions/Comments:

The test is not intended for the judging of day-to-day glycaemic control.  HbA1c values are not suitable for the diagnosis of gestational diabetes. In rare cases of rapidly-evolving Type 1 diabetes, the acute increase in glucose concentration may not be reflected in the HbA1c value.  Diabetes mellitus must be diagnosed based on plasma glucose concentrations and/or typical clinical symptoms.

Care must be taken when interpreting any HbA1c result from individuals with Hb variants, as abnormal haemoglobins may affect the half-life of RBCs and/or in vivo glycation rates.  If it is suspected that the presence of Hb variants affects the correlation between HbA1c value and glycaemic control, consider evaluation by alternative diagnostic tests e.g. fasting plasma glucose, fructosamine measurement.

Glycated HbF is not detected by the HbA1c assay, but is measured as part of the total Hb assay.  As such, specimens containing high (>10%) levels of HbF may result in lower than expected HbA1c values.

Any cause of shortened RBC survival will reduce their exposure to glucose with a consequent decrease in HbA1c value.  Caution should be used when interpreting HbA1c results from patients with these conditions, and alternative methods should be considered to diagnose, monitor or manage diabetes mellitus.

Additional Information:

Glycated haemoglobin (HbA1c) provides an accurate and objective measurement of glycaemic control over a period of months.  HbA1c reflects the integrated glucose control of the life an erythrocyte (120 days), although the estimate is weighted by changes in the glucose level in the month preceding the measurement.

Interferences:

There is no significant effect on test results from the following:

• Conjugated / unconjugated bilirubin up to 1000 µmol/L
• Intralipid concentration up to 500 mg/dL
• Glucose concentration up to 111 mmol/L
• Rheumatoid factors up to 750 IU/L