HbA1c, Libre, alternatives to HbA1c

[LittleGreyCat]

Posted here because this seems to be the area for most of the topic.
However it does stray all over the place.

Starting point: my Libre consistently gives an HbA1c of 5.9%.
My last two HbA1cs were 7.3% and 7.0%
So I am researching possible reasons for the difference.

Latest test included a full Blood Count which showed anaemia.
Anaemia is associated with HbA1c inaccuracies.


Place holder this morning as I assemble the links I found on my mobile phone into a coherent (I hope) whole.

{Back in a while}

 

[EllieM]

Posted here because this seems to be the area for most of the topic.
However it does stray all over the place.

Starting point: my Libre consistently gives an HbA1c of 5.9%.
My last two HbA1cs were 7.3% and 7.0%
So I am researching possible reasons for the difference.

Latest test included a full Blood Count which showed anaemia.
Anaemia is associated with HbA1c inaccuracies.


Place holder this morning as I assemble the links I found on my mobile phone into a coherent (I hope) whole.

{Back in a while}

See if your doctor will give you a fructosamine test instead.
The other reason for the inaccuracy would be if your libre consistently read low, but am assuming you have already tested it against a glucometer and found it accurate?

But honestly, as cgms become more common, I feel that time in range will become more significant than hba1c, at least for the patient, if not for the medical professionals.

 

[LittleGreyCat]

See if your doctor will give you a fructosamine test instead.
The other reason for the inaccuracy would be if your libre consistently read low, but am assuming you have already tested it against a glucometer and found it accurate?

But honestly, as cgms become more common, I feel that time in range will become more significant than hba1c, at least for the patient, if not for the medical professionals.

One of the links I will be posting (hopefully) was a slide pack from Imperial College which recommended against the use of a fructosamine test because there was no established base line against which to asses the results.

It seemed to conclude that BG monitoring was more accurate, but it was a slide pack with a lot of long words so I mainly looked at the pictures.

 

[EllieM]

One of the links I will be posting (hopefully) was a slide pack from Imperial College which recommended against the use of a fructosamine test because there was no established base line against which to asses the results.

It seemed to conclude that BG monitoring was more accurate, but it was a slide pack with a lot of long words so I mainly looked at the pictures.

Interesting, I would argue that BG monitoring is more accurate than hba1c also, particularly if it is via cgm. 30 years ago the NHS was certainly happy to use fructosamine to monitor my control during pregnancy...

 

[In Response]

I have no idea which is most accurate but, given the number of estimates wrt diabetes (carbs in good are estimates, blood sugar meters are not 100% accurate) and there are lots of things outside our control that can affect our blood sugars, I don’t get hung up,on accurate- I focus on trends.
The other thing I consider is Time in Range (TIR).
I think it is better to have a higher TIR than a lower HbA1C which, as someone managing their diabetes with insulin, could be caused by hypos.

 

[LittleGreyCat]

I will update this as I find more information
Links here:
https://www.imperial.nhs.uk/~/media...udy-afternoon-19-october-2017/hba1c.pdf?la=en
The "What interferes with HbA1c" section is very interesting.

As you can see the HbA1c value can be increased by iron and Vitamin B12 deficiency.

"
We do not advocate measurement of
fructosamine
– it is not validated as a measure of glycaemia
i.e. we do not know what the target should be
– it is affected by CKD and proteinuria
– assays are imprecise
"
Which certainly casts doubts over the utility of fructosamine.

"
Monitoring
–Home blood glucose monitoring
•7-point profile gives a good indication of control in most individuals
–Continuous glucose monitoring
•in more complex cases, e.g. insulin treated, referral to a Diabetologist for CGM may be warranted (ICHNT team happy to receive referrals)
"

That seems to suggest that the values from Libre/Libre 2 should possibly be a better guide.

 

[LittleGreyCat]

From:
https://www.nice.org.uk/guidance/ng28/chapter/Recommendations#hba1c-measurement-and-targets

"
1.6.7For adults with type 2 diabetes managed either by lifestyle and diet, or by lifestyle and diet combined with a single drug not associated with hypoglycaemia, support the person to aim for an HbA1c level of 48 mmol/mol (6.5%). For adults on a drug associated with hypoglycaemia, support the person to aim for an HbA1c level of 53 mmol/mol (7.0%). [2015]

1.6.8In adults with type 2 diabetes, if HbA1c levels are not adequately controlled by a single drug and rise to 58 mmol/mol (7.5%) 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 (7.0%) and
  
  
• intensify drug treatment. [2015]
  

"

So my last 2 results of 7.3% and 7% are high for diet, exercise and Metformin.
Target should be 6.5%.

Possibly I should be starting a second drug (but which?).

However if the Libre is correct I am maintaining 5.9% to 6% which is pretty good.
I could even relax my strict regime occasionally for a treat.

Depending on the correct results, then, it is "drugs or chips".
Quite a big difference and a very emotional one as well.
Either I am holding back the night or I am on the slippery downward slope.

 

[Brunneria]

Have you been doing fingerprick tests alongside the Libre to gauge its accuracy?

All my Libre 1s underestimated my HbA1c significantly, and the Libre readings were usually over 1 mmol/l lower than my fingerpricks.
Have only used 1 x Libre 2 so far, which was much closer to my fingerprick tests - and gave a predicted HbA1c much more aligned with previous HbA1cs.
Too early to assume that the L2 is going to be consistently more accurate than L1, for me.

 

[LittleGreyCat]

Have you been doing fingerprick tests alongside the Libre to gauge its accuracy?

All my Libre 1s underestimated my HbA1c significantly, and the Libre readings were usually over 1 mmol/l lower than my fingerpricks.
Have only used 1 x Libre 2 so far, which was much closer to my fingerprick tests - and gave a predicted HbA1c much more aligned with previous HbA1cs.
Too early to assume that the L2 is going to be consistently more accurate than L1, for me.

I do check and sometimes the L1 was out; high and low at times but generally settled down after a few days.

The L2 seems better.

The BC showing anaemia is what started me off on my current chase, because this can artificially raise HbA1c.

7.0% equates to an average BG of 8.5 mmol/L
5.9% equates to 6.8 mmol/L

So the difference between finger prick and Libre reading would have to be 1.7 mmol/L low for the Libre on average to explain the difference.
I could perhaps believe up to one full unit, but nearly two full units on average seems too much of a stretch.

As I said further up, the difference is between pretty good control and being in the area for a second medication.