Discrepancy Between Fingertip Glucose Levels and HbA1c in Diabetes. 2023 case report

pattismith

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this is something I learn recently while controling my own blood glucose:

Microvascular dysfunction can cause a gap between glycemia at the fingertip (low) and veinous glycemia (high).





TAP_March_2023-127-128.pdf (turkarchpediatr.org)

Discrepancy Between Fingertip Glucose Levels and HbA1c in an Adolescent with Diabetes

Pseudohypoglycemia is a term used to describe an artificially low blood glucose level. (...), peripheral vasoconstriction caused by Raynaud’s phenomenon, acrocyanosis, and shock may cause capillary measurement errors.5

Raynaud’s phenomenon is a condition that causes vasoconstriction due to the upregulation of alpha-adrenergic receptors in stressful situations such as exposure to cold weather, anxiety, and fear. It usually causes coldness in the fingers and toes, followed by changes in skin color.6

Disruption in digital microcirculation due to vasoconstriction causes prolongation of blood circulation time in capillaries and increased glucose consumption by tissues.4,6
 

Judee

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Microvascular dysfunction can cause a gap between glycemia at the fingertip (low) and veinous glycemia (high).

I don't have diabetes (that I know of) but I do have Reynaud's. I have had to do a finger poke a few times in the past. Some websites said that finger pokes can destroy touch sensitivity over time. :(

I did find this site a while back that talks about other places that are acceptable for taking blood so I wonder if a person could avoid the issue discussed in that article by sticking the Thenar or Hypothenar instead.

https://www.diabetesincontrol.com/f...sites-with-same-response-time-as-finger-tips/

And as the article says, "All who now wish to test from these new sites should check with their doctor to be certain there are no special metabolic considerations that would preclude you from testing on these new areas."

I guess it would be best to show your doctor both articles.
 

linusbert

Senior Member
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Some websites said that finger pokes can destroy touch sensitivity over time. :(
that is true... but it also comes back when not pricking after a while. i think its like workers hands. they become rough more insensitive but when not doing rough work anymore, they become "normal" over time again.
 

pamojja

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There are other reason for discrepancies between glucose and HbA1c: Though in case of high dose vitamin C, as I take, HbA1c will be lowered.

Journal of the New Zealand Medical Association, 23-August-2002, Vol 115 No 1160

Glycohaemoglobin and ascorbic acid

Copplestone et al1 (http://www.nzma.org....al/115-1157/25/) identified misleading glycohaemoglobin (GHb) results due to a haemoglobin variant (Hb D Punjab) and listed a number of other possible causes for such false results (ie, haemolytic anaemia, uraemia, lead poisoning, alcoholism, high-dose salicylates and hereditary persistence of foetal haemoglobin).

We have observed a significant "false" lowering of GHb in animals and humans supplementing ascorbic acid (AA) at multigram levels. Mice receiving ~7.5 mg/d (equivalent to > 10 g/day in a 70 kg human) exhibited no decrease in plasma glucose, but a 23% reduction in GHb.2 In humans, supplementation of AA for several months did not lower fasting plasma glucose.3,4 We studied 139 consecutive consenting non-diabetic patients in an oncology clinic. The patients had been encouraged as part of their treatment to supplement AA. Self-reported daily intake varied from 0 to 20 g/day. The plasma AA levels ranged from 11.4 to 517 µmol/L and correlated well with the reported intake. Regression analysis of their GHb and plasma AA values showed a statistically significant inverse association (eg, each 30 µmol/L increase in plasma AA concentration resulted in a decrease of 0.1 in GHb).

A 1 g oral dose of AA can raise plasma AA to 130 µmol/L within an hour and such doses at intervals of about two hours throughout the day can maintain ~230 µmol AA/L.5 Similar levels could also be achieved by use of sustained-release AA tablets. This AA concentration would induce an approximate 0.7 depression in GHb. The GHb assay used in our study, affinity chromatography, is not affected by the presence of AA.3 Thus, unlike the case with Hb D Punjab, our results were not caused by analytical method artifact. More likely, the decreased GHb associated with AA supplementation appears related to an in vivo inhibition of glycation by the elevated plasma AA levels, and not a decrease in average plasma glucose.3 If this is true, the effect has implications not only for interpretation of GHb but also for human ageing, in which glycation of proteins plays a prominent role in age-related degenerative changes.

A misleading GHb lowering of the magnitude we observed can be clinically significant. Current recommendations for diabetics suggest that GHb be maintained at 7, a level that is associated with acceptable control and decreased risk of complications; when GHb exceeds 8, re-evaluation of treatment is necessary.6 Moreover, relatively small increases in average blood sugar (ie, GHb) can accompany adverse reproductive effects. A difference in mean maternal GHb of 0.8 was found for women giving birth to infants without or with congenital malformations.7 In either of these circumstances, an underestimation of GHb could obscure the need for more aggressive intervention.

Vitamin usage is common in New Zealand and after multivitamins, AA is the most often consumed supplement.8 Moreover, diabetics are encouraged to supplement antioxidants, including AA. Thus, it seems prudent for primary care health providers to inquire regarding the AA intake of patients, especially diabetics, when using GHb for diagnosis or treatment monitoring.

Cheryl A Krone
Senior Research Scientist
John TA Ely
Director
Applied Research Institute
PO Box 1925
Palmerston North

References:

  • Copplestone S, Mackay R, Brennan S. Normal glycated haemoglobin in a patient with poorly controlled diabetes mellitus and haemoglobin D Punjab: implications for assessment of control. NZ Med J 2002;115(1157). URL: http://www.nzma.org....al/115-1157/25/
  • Krone CA, Ely JTA. Vitamin C and glycohemoglobin revisited. Clin Chem 2001;47(1):148.
  • Davie SJ, Gould BJ, Yudkin JS. Effect of vitamin C on glycosylation of proteins. Diabetes 1992;41(2):167–73.
  • Paolisso G, Balbi V, Bolpe C, et al. Metabolic benefits deriving from chronic vitamin C supplementation in aged non-insulin dependent diabetics. J Am Coll Nutr 1995; 14(4):387–392.
  • Lewin S. Vitamin C: Its Molecular Biology and Medical Potential. New York: Academic Press; 1976.
  • Kenealey T, Braatvedt G, Scragg R. Screening for type 2 diabetes in non-pregnant adults in New Zealand: practice recommendations. NZ Med J 2002;115(1152):194–6.
  • Rosenn B, Miodovnik M, Dignan PS, et al. Minor congenital malformation in infants of insulin-dependent diabetic women: association with poor glycemic control. Obstet Gynecol 1990;76:745–9.
  • Allen T, Thomson WM, Emmerton LM, Poulton R. Nutritional supplement use among 26-year-olds. N Z Med J 2000;113(1113):274–7.

Also slightly differently lifecycles of red blood cells can falsify. The older they get, the more they accumulate.
 

linusbert

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i dont get it, it doesnt look like "falsefied"... it actually looks like a effective treatment to prevent glycation of proteins and haemoglobin. this is a big positive.
of course if A1C is used as sole instrument for control of blood sugar control in diabetes, this might indicate better control of sugar when it isnt.

but i wouldnt use A1C anyways. its unreliable for me.
just measure early morning and maybe 2h after supper and go with those values.
 

Judee

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i dont get it, it doesnt look like "falsefied"... it actually looks like a effective treatment to prevent glycation of proteins and haemoglobin. this is a big positive.

I was wondering that too but my brain is too tired to read the whole thing and process right now.
 

pattismith

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3,988
but only in raynauds?
any microvascular dysfunction with poor blood flow I guess...

In my case, I had Small Fiber Neuropathy in 2019 that resolve after corticosteroid treatment;

Then I got my covid vaccines and got microvascular dysfunction; I don't seem to have SFN back, so i guess the damage is different.

I don't have Raynaud phenomenon nor acrocyanosis, however I noticed a difference between my finger tip glucose level and my venous level. I tried to test glucose at the ear capillaries as well, but it was not different from the fingertip...
 

pamojja

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i dont get it, it doesnt look like "falsefied"... it actually looks like a effective treatment to prevent glycation of proteins and haemoglobin. this is a big positive.

but i wouldnt use A1C anyways. its unreliable for me.
just measure early morning and maybe 2h after supper and go with those values.

Yes and no. As a prediabetic I would exactly want to know, how present diet and supplements is affecting my insulin resistance. HbA1c, fasting glucose, etc. can all be influenced/falsified by too many factors.

With average glucose I can check how much there is deviation from HbA1c. For that I do check fasting and postprandial glucose after each meal (highest peak after 1hr for me, 2 meals a day), and the average between lowest and highest to calculate HbA1c (which, of course is only an approximation), and find a divergence of 0.7%Hb from the calculated to the meassured, in average. With additional insulin or C-Peptide meassurements I can calculate my fluctuating HOMA insulin-resistance, to look at a more likely picture.

Despite having taken 25 g/d of ascorbic acid a day, and which should result actually in at least 1.0% lowering of GHb,
Most probable factor in my case: I can't confirm a similiar increase in serum ascorbate, as seen in above study. Which is easily explained by different bio-chemical-individualities, already outlined in the book of Linus Pauling in respect to vitamin C. Some need nothing at all, some need multiple grams for avoiding diseases.
 

linusbert

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Yes and no. As a prediabetic I would exactly want to know, how present diet and supplements is affecting my insulin resistance. HbA1c, fasting glucose, etc. can all be influenced/falsified by too many factors.
if u want to do that, i'd rather get a flash continous glucose monitor. like dexcom or freestyle libre.
 
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