HbA1c for Monitoring

Purpose:
HbA1c is used for both the diagnosis (Type 2) and monitoring of diabetes (Type 1 & 2) and as part of the NHS England Health Check for subjects that on initial screen are identified as having a risk of developing diabetes.

HbA1c is commonly used to monitor glycaemic control in both Type 1 and Type 2 diabetes as it provides a measure of average plasma glucose over the preceding 8 – 12 weeks.

Type 2 diabetes in adults: management. NICE guideline [NG28]
Recommendations: HbA1c measurement and targets

HbA1c levels in adults with type 2 diabetes should be measured every: 3 to 6 months (tailored to individual needs) until HbA1c is stable on unchanging therapy or 6 months once the HbA1c level and blood glucose lowering therapy are stable.
HbA1c should be measured using methods calibrated according to IFCC standardisation.
NICE has produced a patient decision aid on agreeing HbA1c targets, which also covers factors to weigh up when discussing HbA1c targets with patients.
For adults whose type 2 diabetes is managed either by lifestyle and diet, or lifestyle and diet combined with a single drug not associated with hypoglycaemia, aim for an HbA1c level of 48 mmol/mol. For adults on a drug associated with hypoglycaemia, aim for an HbA1c level of 53 mmol/mol.
In adults with type 2 diabetes, if HbA1c levels are not adequately controlled by a single drug and rise to 58 mmol/mol or higher: reinforce advice about diet, lifestyle and adherence to drug treatment and support the person to aim for an HbA1c level of 53 mmol/mol and intensify drug treatment.

Scope:
Weqas provides 3 different Programmes for HbA1c based on the clinical utility of the HbA1c test. This programme aims to cover the clinically relevant ranges for the monitoring of diabetes, including the assessment of the analytical measuring range. The programme is suitable for all Laboratory methods and for Point of Care testing (POCT) applications used for monitoring diabetes.

A separate programme is available for Laboratories using HbA1c for diagnosis as well as a separate programme for the assessment of organisations undertaking population health check screening and the NHS England Health Check Programme. The latter is specifically designed to assess POCT applications in a combined Lipid and HbA1c programme. Please see the Weqas POCT HealthChecks EQA Programme for further information.

Fresh EDTA whole blood from individual diabetic patients and healthy volunteers are distributed monthly/bi-monthly. These samples reflect the wide range of HbA1c seen in healthy individuals and in Diabetic patients. Samples from volunteers and diabetic patients are distributed to ensure that the concentration range is appropriate for diabetes patient monitoring.

The HbA1c reference target values in the Weqas programme are assigned using IFCC secondary reference methods in an IFCC network laboratory. The programme allows for the assessment of the organisation’s and method’s performance, including linearity, trueness, bias, and imprecision. The acceptable performance specification used in this programme reflects the clinical requirement for the monitoring of diabetes and is less stringent than the Weqas Programme for HbA1c Diagnosis.

Key Features:

Whole blood samples are collected from healthy volunteers and patients with Type II Diabetes.
Samples cover non-diabetic, diagnostic cut-off level, (48mmol/mol Hb), pathological and analytical ranges.
Scoring based on Milan Model 3 performance specification.
Programme assesses both laboratory and method performance, including trueness, bias, within and between batch imprecision.
Trueness is assessed using the IFCC secondary reference methods.