How does a hba1c work?

[Polska_Gurom]

How do they know the past 3 months from one test, just curious lol.

 

[MissMuffett]

I googled it for a simplified explanation and this is what came up:

An A1C test can show your average glucose level for the past three months because:

• Glucose sticks to hemoglobin for as long as the red blood cells are alive.
• Red blood cells live about three months.

Hope this helps

 

[KennyA]

How do they know the past 3 months from one test, just curious lol.

Glucose in the blood binds with and damages red blood cells. There's a category of haemoglobin (A) that's around 90% of all haemoglobin and comparatively easy to count, and the test can count how many of those red blood cells have been glycated. HbA1c is the major glycated component, and the results correlate fairly well with average blood glucose.

Red blood cells live about 90-120 days maximum, so any RBCs from before then will probably have already been cleared up. The test is skewed towards the last month - 50% of the value reflects the 30 days prior to the test, and only 10% the initial 30 days of red blood cell life.

It's not spot on, there is some variation between tests, and around test accuracy (I've had a completely off the wall result recently, which was proved very wrong when checked against a full lab test), but these are usually relatively small amounts. It's why they repeat the HbA1c for T2 diagnosis if the initial result is close to 48. There's also a number of other conditions - iron deficiency, pregnancy, red cell disorders etc, that can affect the test.

So, not a perfect and totally accurate test, but good enough for most purposes.

Source for the above: Bilous and Donnelly, Handbook of Diabetes.

[edited for clarity]

 

[Polska_Gurom]

Glucose in the blood binds with and damages red blood cells. There's a category of haemoglobin (A) that's around 90% of all haemoglobin and comparatively easy to count, and the test can count how many of those red blood cells have been glycated. HbA1c is the major glycated component, and the results correlate fairly well with average blood glucose.

Red blood cells live about 90-120 days maximum, so any RBCs from before then will probably have already been cleared up. The test is skewed towards the last month - 50% of the value reflects the 30 days prior to the test, and only 10% the initial 30 days of red blood cell life.

It's not spot on, there is some variation between tests, and around test accuracy (I've had a completely off the wall result recently, which was proved very wrong when checked against a full lab test), but these are usually relatively small amounts. It's why they repeat the HbA1c for T2 diagnosis if the initial result is close to 48. There's also a number of other conditions - iron deficiency, pregnancy, red cell disorders etc, that can affect the test.

So, not a perfect and totally accurate test, but good enough for most purposes.

Source for the above: Bilous and Donnelly, Handbook of Diabetes.

[edited for clarity]

Thanks mate

 

[Antje77]

Glucose in the blood binds with and damages red blood cells.

I suppose you mean excessive glucose in the blood damages red blood cells?
Without glucose in the blood you are dead, you need glucose in your blood.

Otherwise, I agree with your informative post.

 

[KennyA]

I suppose you mean excessive glucose in the blood damages red blood cells?
Without glucose in the blood you are dead, you need glucose in your blood.

Otherwise, I agree with your informative post.

No, that's glucose doing what glucose does, although I completely agree that a normal level of blood glucose is necessary. Excess blood glucose will/would have an excess impact. B&D say:

"Haemoglobin A comprises over 90% of most adult haemoglobin and is variably glycated by the non-enzymatic attachment of sugars"