Glycated hemoglobin (HbA1c) continues to have a central role in diabetes care, even more so in under-resourced countries where CGM (continuous glucose monitoring) is not accessible to the majority. There is strong evidence that HbA1c indicates much of the level of risk of developing diabetes complications.
 
HbA1c has a standardized reference method and procedure set by the IFCC (International Federation of Clinical Chemistry), and the availability of point-of-care measurement in clinics and in outreach and remote settings makes this test more widely available (de Bock et al, 2022). 

Point-of-care (PoC) HbA1c testing using a ‘desktop’ machine provides immediate results (test takes around 6 minutes depending on the machine) which facilitates clinical decision making and treatment changes during a clinic appointment. PoC HbA1c has shown to be an accurate method comparable to IFCC certified laboratory tests. 

In 2007, the IFCC recommended that IFCC HbA1c be expressed as mmol HbA1c/mol Hb to avoid confusion between NGSP (National Glycohemoglobin Standardization Program) results which are measured in %. You can read more about IFCC standardisation and conversion from % to mmol/mol here. Most PoC machines display both % and mmol/mol or can be set to read one or the other.

ISPAD (2022) guidelines recommend that every young person with diabetes should have four HbA1c measurements per year (at 3-month intervals) and perform and record daily SMBG. 

What is HbA1c

HbA1c results from the attachment of glucose to the haemoglobin β-chain in a process known as glycation. It is dependent on the concentration of blood glucose and the lifespan of the erythrocyte (red blood cell).  As the average erythrocyte lifespan is approximately 120 days, HbA1c acts as a substitute marker of glucose concentration during the previous 8–12 weeks. As a result of the continuous turnover of erythrocytes, it is estimated that only 50% of an HbA1c value represents glucose concentrations in the previous 30 days, while 40% represents exposure in the previous 31–90 days and 10% in the previous 91–120 days.

Glycaemic Targets for children and young people with diabetes (ISPAD, 2022 guidelines)

• HbA1c <53 mmol/mol (<7.0%)
• HbA1c <48 mmol/mol (6.5%) for the remission phase or early stage 3 diabetes “honeymoon” period; and in young people with diabetes with access to advanced technology combined with a highly skilled health care and education
• Capillary blood glucose (SMBG) between 4 - 10 mmol (70–180 mg/dl)
• Fasting SMBG between 4– 8 mmol/L (70 - 144mg/dl)
• Targets need to be individualised based on circumstances (e.g. access to SMBG supplies, psychosocial health concerns etc.)

• Clinical states associated with altered rates of haemoglobin turnover or erythrocyte survival will affect HbA1c measurements, either ‘falsely’ increasing or decreasing HbA1c levels (see table 1) and therefore affect clinical utility.
• There are some rare haemoglobinopathies and conditions such as haemolytic anaemia which can give artificially low HbA1c levels. These should be considered if a surprisingly low HbA1c level is found, after the test has been repeated and the result is still low.
• There is good evidence that, on average, African-origin people have slightly higher HbA1c levels than European-origin people for the same level of blood glucose (Chalew et al, 2019). This may not be associated with an increase in complications (Staimez et al, 2020), but further studies are needed.

• Accuracy of Point-of-Care testing- the most common cause of an unusually low HbA1c value in a young child or adult with diabetes is an inaccurate or poorly maintained machine and/or lack of quality control. Be aware of factors that can affect accuracy:

1. HbA1c cartridges have not been stored according to manufactures recommendations
2. Machine has not been maintained according to manufactures recommendations
3. No or inadequate quality controls performed (or results have not been checked against normal values)  
4. Inadequate calibration (e.g. using wrong calibration card)
5. Point-of-care machine – there are variation in accuracy and precision between machines

• Repeat the test unless you are very confident that the child/young adult:

1. has excellent blood glucose control
2. is in the 'honeymoon' phase of type 1 diabetes
3. has type 2 diabetes
4. has another type of diabetes (e.g., monogenic)
5. has an 'atypical’ form of diabetes rather than classic type 1 diabetes

• Compare the result with self-glucose monitoring level (SMBG) – do they correspond?
• Assess if the child/young adult has frequent moderate or severe (unable to self-treat, unresponsive or unconscious) hypoglycaemic episodes and may need insulin dose adjustment and education
• Perform all necessary maintenance and quality control checks according to manufacturer’s instructions
• Check the results of the control solution against the range shown on the Normal or Abnormal control solution card (see images page 4 if using the Siemens machine), depending which control solution you are using
• Ensure cartridges are stored in the fridge, are not expired!
• Ensure reconstituted control solution are stored in the fridge (2-8 °C), are in date and are only used up to 3 months after they have been first opened (write the date of first use on the bottle). Don’t leave them at room temperature for more than 30 minutes!
• Consider if your machine is malfunctioning – contact us!

What to do if the result has disappeared from the screen?
You can recall the result of HbA1c Patient Test, Control test, and Calibration Data by following the instructions on this link: https://pep.siemens-info.com/en-us/recall-hba1c-calibration