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What can give false lower A1C
- Thread starter lorib64
- Start Date
Possibly.
First thing is that the HbA1c counts glycated red blood cells, and does not measure the same thing (blood) as the fingerprick tests, and neither of those measure the same thing (interstitial fluid) as the CGM. So they're not the same test and aren't really directly comparable. In addition the HbA1c is assessing your blood cells over the last three months (because that's how long red blood cells live generally) and is not a "right now" snapshot like the CGM or fingerprick.
All these tests have an allowable error, usually 5% for 95% of tests.
CGMs are great for showing patterns and trends, but my experience (via calibration from fingerpricks) has been that their given values are not to be trusted.
Averaging tests can be misleading, because you're only averaging what you record, so you don't include what's happening when you're not testing. Like trying to work out the average of your driving speed by looking at the speedometer three or four times during an hour's driving.
You may therefore build in skew - for example, if a high proportion of your tests are first thing in the morning fasting tests, and you have dawn phenomenon, those may be the highest BG levels you'll have all day. Add in the +2 hr post-meal tests, and you are possibly skewing further towards recording higher numbers.
So it's hard to say. Of the three, I would trust the HbA1c most unless you have a good reason not to.
First thing is that the HbA1c counts glycated red blood cells, and does not measure the same thing (blood) as the fingerprick tests, and neither of those measure the same thing (interstitial fluid) as the CGM. So they're not the same test and aren't really directly comparable. In addition the HbA1c is assessing your blood cells over the last three months (because that's how long red blood cells live generally) and is not a "right now" snapshot like the CGM or fingerprick.
All these tests have an allowable error, usually 5% for 95% of tests.
CGMs are great for showing patterns and trends, but my experience (via calibration from fingerpricks) has been that their given values are not to be trusted.
Averaging tests can be misleading, because you're only averaging what you record, so you don't include what's happening when you're not testing. Like trying to work out the average of your driving speed by looking at the speedometer three or four times during an hour's driving.
You may therefore build in skew - for example, if a high proportion of your tests are first thing in the morning fasting tests, and you have dawn phenomenon, those may be the highest BG levels you'll have all day. Add in the +2 hr post-meal tests, and you are possibly skewing further towards recording higher numbers.
So it's hard to say. Of the three, I would trust the HbA1c most unless you have a good reason not to.
Yes it would, in the period after donating.
You donate the glycated blood cells and produce new ones to replace them.
Some blood cell conditions and aneamia can also give false hba1c results.
