Can you help with a discrepancy

The finger prick readings are only your BG at the time youprick your finger.
Hb1AC is an average at all time.
For example, you may peak earlier or later than your post prandial finger prick or your BG may rise and fall over night.

Tagging @Bluetit1802 because she has an interesting thread relating to her HBA1C discrepancy.

There are other conditions that can affect HBA1C like anaemia so it would be worth talking to your healthcare people.

It is frustrating when your HBA1C does not reflect how well you are doing with the factors within your control. But please trust you are doing the best for your health long term. I envy your home meter results.

Speedbird said:

Morning everyone,
Can you help?


Discrepancies in Hba1c readings

My eight daily blood glucose monitor results give consistent readings of between between 3.5 and 8 (using the Codefree monitor which I believe marks high). My sugar app has averaged this out to 37.4 over the past 6 months or more. However my 6 monthly Hba1c review at the doctors are returning a much higher reading of 48 ? Can anybody explained the discrepancy between the two figures?

Thank you

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As @Alison Campbell said, I have a similar problem that has been on-going for around 4 years. I am not the only one on this forum by any means.

I would first say that in my case it is the finger prick testing that is the more accurate. They tally with the home HbA1c tests that I have done at the same time as the official test, and are roughly in line with the Libre that I use part time and leading up to my official HbA1c test. (after taking account of the Libre's tendency to read a bit low in my case)

If you have red blood cells that are not standard (in other words, do not fall within the average of the general population) then your HbA1c can be inaccurate - either falsely high or falsely low. This can be because of a variety of things, including iron deficiency, whether your haematocrit levels are low or high, certain types of anaemia, certain thyroid issues, or simply because your red blood cells live longer than the standard average of 120 days, or live less than this average. You can check if you have iron deficiency, high or low haematocrits, anaemia, or thyroid issues, but sadly we cannot know how long our red blood cells live. The HbA1c assumes everyone has the standard of around 120 days.

Last summer I managed to get my GP to agree with me. This was the thread I wrote at the time.

https://www.diabetes.co.uk/forum/threads/2-hba1cs-2-labs-1-blood-sample.154627/

My GP has now arranged for me to have my blood from the same blood draw analysed by the 2 different labs on each occasion that I have the test. It hasn't completely solved my problem, but has gone somewhere towards it.

Meanwhile, I am happy my own personal data is the most accurate.

PS. also don't forget when trying to estimate your HbA1c that it is weighted towards the last 2 or 3 weeks and isn't an average of the last 3 months.

Speedbird said:

Thank you for th


Thank you for that. I am quite prolific in testing my blood sugar. If I see it is rising then I will test more. More often than not I will test before bedtime and then of course first thing in the morning. So some days I will be finger pricking up to 10 or 12 times a day. What is more disappointing is that the same discrepancy happened in my review 6 months previously. Somehow it doesn’t tally.
I always thought that the finger pricking is more accurate. Perhaps not.

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Hi @Speedbird,

I really get your frustration. A difference of 10 mmol is a lot. I've also experienced a difference between glucometer results and HbA1c, but it is not quite as large as yours.

Depending on how long-lived your red blood cells are, your HbA1c can be considerably off -- somewhere in the neighborhood of 6 mmol. Here is a link to the article:
http://www.bloodjournal.org/content/112/10/4284?sso-checked=true#ref-32
https://www.healthline.com/health/type-2-diabetes/ac1-test#understanding-the-results

Have you compared your glucometer blood sugar reading with the one taken at the doctor's office while getting your HbA1c test to gauge the accuracy of your glucometer? Also using a freestyle libre or a dexcom for 2 weeks might give you additional information.

Edited for clarity.

One way to check your meter is to use it at the same times as a blood test is taken, then ask the nurse if she can do a check with a meter there and then, or wait until your results come back - assuming that you get a blood glucose check on the blood taken.

Speedbird said:

Can anybody explained the discrepancy between the two figures?

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It is said that the HbA1c reflects something of an 8 - 12 week average.

The theory behind the A1c test is that our red blood cells live an average of three months, so if we measure the amount of sugar stuck to these cells (which is what the hemoglobin A1c test does), it will give us an idea of how much sugar has been in the blood over the previous three months. The number reported in the A1c test result indicates the percentage of hemoglobin that has become glycated (stuck to sugar).

While this sounds good in theory, the reality is not so black and white. The main problem is that there is actually a wide variation in how long red blood cells survive in different people. Researchers found that the lifetime of hemoglobin cells of diabetics turned over in as few as 81 days, while they lived as long as 146 days in non-diabetics.

It's comparing apples with oranges.

ziggy_w said:

Hi @Speedbird,

I really get your frustration. A difference of 10 mmol is a lot.

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Just for clarity, mmol/mol readings for HbA1cs are different to mmol/L readings for blood glucose.
Compare
mmol/mol HbA1c = % HbA1c = average blood glucose
31 = 5 = 5.4
42 = 6 = 7
53 = 7 = 8.5

For someone thinking blood sugar monitor readings, 10 mmol/L is a lot. Converting HbA1cs to roughly 1.5 mmol/L difference is less scary
This is not to discount concern over variation, or the prudence of keeping blood cell glycation low.
Geoff

librarising said:

Just for clarity, mmol/mol readings for HbA1cs are different to mmol/L readings for blood glucose.
Compare
mmol/mol HbA1c = % HbA1c = average blood glucose
31 = 5 = 5.4
42 = 6 = 7
53 = 7 = 8.5

For someone thinking blood sugar monitor readings, 10 mmol/L is a lot. Converting HbA1cs to roughly 1.5 mmol/L difference is less scary
This is not to discount concern over variation, or the prudence of keeping blood cell glycation low.
Geoff

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Hi @librarising,

Thanks for your always helpful information. In this case, I was refering to HbA1c rather than blood sugar readings. So, proabably I should have used mmol/mol rather than just mmol for clarity. The OP was expecting an HbA1c of roughly 38 based on blood sugar readings, but the lab results were 48 -- so a difference of 10 mmol/mol. Or am I misunderstanding something?

Speedbird said:

Thank you for th


Thank you for that. I am quite prolific in testing my blood sugar. If I see it is rising then I will test more. More often than not I will test before bedtime and then of course first thing in the morning. So some days I will be finger pricking up to 10 or 12 times a day. What is more disappointing is that the same discrepancy happened in my review 6 months previously. Somehow it doesn’t tally.
I always thought that the finger pricking is more accurate. Perhaps not.

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As a diabetic, not as professional opinion or advice: Some glucose meters can be out by 15% in their accuracy. Why do 10 to 12 blood glucose readings per day? Is that really helpful? Does it change what you do? And how are your fingers going to survive that amount of prickings over the years?
As others above have said you cannot directly equate blood sugar readings to the HBA1C reading. Getting upset about it will not help you. Talk with your GP about whether there is any reason for your HBA1C result be affected by the causes as listed by @ziggy_w and @Bluetit1802 and if there is no reason, consider what is suggested by your GP.

Just for clarity, to add to my original post number #5

My normal lab uses an HbA1c analysis machine called a High Performance Liquid Chromatography.

The Salford lab where my blood is also being analysed uses an HbA1c analysing machine called an Affinity Chromatography. This machine does some separating that enables it to take account of certain haemoglobin variances, I think of the genetic variety. I don't understand it at all. If you Google these two machines you will see there are several research documents and quite a bit of information, but it is way above my head scientifically. You may have more luck interpreting them. My GP had to have conversations with the consultant biochemist at the lab as she was also clueless.

My HbA1c has been around 10 points higher on each 6 monthly test for the last 4 years, possibly even on diagnosis but of course I have no personal data from that time as I was slow in getting my own meter..

In defence of my finger pricking meters, yes, they may be up to 15% higher or lower, but not all the time. It is swings and roundabouts. Over a period of 4 years they would have averaged out. They also tally with the A1cNow (home HbA1c test) and the Libre after taking account of the Libre reading a bit low. I do convert them all to the same measurement units

I have had similar problems. I think I have relatively tested in the top percentile for between 1.5 and 2 years, using 6 different meters, often 2 or 3 at the same draw. All of my meters show average numbers of circa 4.3 / 4.4 for both fasting and post prandial settings. I have used Freestyle Libre's which always read low (estimated HbA1c's of 22 for example), but I use these to see if I am spiking. On the A1CNow + unit I have tested at an average of 31.5% for over a year, about 8 tests (20 pack) - I compare myself to non-diabetics and have never had a higher score than 3. My fbg this morning was 3.9 and just tested 20.47 @ 4.8 (will definitely have fbg in the morning <4.5) but yet my official HbA1c is 38, 18% higher than expected, I never see 6's which the HbA1c says I am averaging at. I have found out that the machine used for my official reading is taken on is called a Biorad D100, thanks @Bluetit1802, your nugget of information suggests I should try with an Affinity Chromatography based machine.

I discussed my situation over the phone with 2 Endo's at Ipswich Hospital where my bloods gets tested, the first was more helpful but the head said your in remission what's the problem, I said can it be right that my numbers have gone from 5's to late 3's early 4's and yet my HbA1c has gone up; the lady explained that I might be higher at different times, I said tested to death at different times on this and that A1CNow+ says 31 with a best of 29 and that Libre showed I am not spiking.

I dream of being in remission and blood result of 38 . Wow that would make me very happy .

Charis1213 said:

I dream of being in remission and blood result of 38 . Wow that would make me very happy .

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Apologies, it can seem ungrateful when others have a deeper struggle, easy to get wrapped up in ones own bubble. You are putting in at least an hour of walking, so very close to what you would like (on some scales you are right of the cusp of remission, for example the DiRECT trial). Any excuse I get I recommend weight training to make a difference, so apologies again for preaching, but how about splitting your hours walk to maybe 45 mins with 15 mins resistance training, weighted or body weight.

I will get to the bottom of my story just as the numbers don't add up, I would accept a discrepancy of up to 10%, but 18% is too much, especially when my wife gets a 32 on the A1cNow and I get a 31, and she has an fbg of 5.2 and I am always low 4's or late 3's, all on the same units. I am going to get private tests for HbA1c on the competing unit, fructosamine test and fasting insulin. Another term for you to research is "discordance". If you have any other conditions such as thyroid problems this can interfere with your results. I have had really low white blood cell counts which luckily for me is due to low inflammation, which might be causing "noise", so you might want to review a full blood count also.

The significant HbA1c discrepancies that several of us report is concerning. The vast, vast majority will never realise that our test results could be so inaccurate, especially the many T2s that never test and have no other data to look at. It does make me wonder how many people have haemoglobin variants but never realise. It can clearly make a big difference - upwards and downwards. How many folk are misdiagnosed, or how many escape diagnosis because of it. How many are taken in by super low HbA1cs on reviews that are skewed?