HbA1c, Libre, alternatives to HbA1c

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 said:

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.

Click to expand...

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.

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.

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 said:

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.

Click to expand...

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.