Notice of HbA1c reference interval and target limit harmonisation at all Awanui Labs effective 1 June 2025.
Earlier this year, we transitioned to the Roche HbA1C methodology as part of a national initiative to harmonise assays across our laboratories. This change was not expected to impact the clinical management of your patients. However, we have received feedback regarding an apparent increase in prediabetes diagnosis.
From 1 June 2025 Awanui Labs will be moving to the updated NZSSD guidelines (soon to be published). We will update both our reference interval for the Roche assay as well as the diagnostic and management thresholds for diabetes and prediabetes to align with the new NZSSD guidelines.
Key Changes:
- All HbA1c assays are now performed on the Roche c513 platform.
- New HbA1C reference interval: <42 mmol/mol
- New diagnostic thresholds:
- 42-47 mmol/mol: High risk of prediabetes
- >=48 mmol/mol: Diagnostic of diabetes mellitus
- New general target for meeting therapeutic goals in a known diabetic: <53 mmol/mol
- Estimated Average Glucose (eAG) will be added to all HbA1C results to aid clinical interpretation. eAG provides an approximate mean glucose concentration (expressed in mmol/L), offering a more intuitive measure for patients and clinicians when comparing to daily glucose monitoring. However, eAG remains dependent on HbA1c measurement accuracy and should not be used in cases of significant Hb variant interference or altered red cell turnover.
These changes will ensure consistency and alignment with best-practice guidelines.
Considerations for Hb Variants and Analytical Limitations
The Roche c513 method, like other HbA1c assays, may be affected by haemoglobin variants (e.g., HbS, HbC, HbE) and certain rare haemoglobinopathies, potentially leading to inaccurate HbA1c results. While the c513 has improved variant detection compared to earlier methods, some interferences remain. In cases where results are inconsistent with the clinical picture, the following approach is recommended:
- Alternative Biomarkers: If an Hb variant is suspected or the HbA1c result does not correlate with clinical findings, consider using fructosamine or glucose-based criteria (fasting glucose, oral glucose tolerance test) to assess glycaemic control.
- Clinical Correlation: Regularly review patient history, ethnicity, and previous HbA1c trends, particularly for patients with known haemoglobinopathies.
- Laboratory Alerts: When an interfering Hb variant is suspected, the laboratory will issue a comment advising alternative assessments.
We appreciate your support in implementing this change. If you have any questions or require further clarification, please do not hesitate to reach out.
Dr Melissa Yssel
Clinical Lead – Chemical Pathology & Illumiscreen
Awanui Group