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Advisor
4xgrandma
Total Posts: 85
Registered on: ‎11-04-2009

Accuracy of A1c test

I recently had an A1c done at my internist.  It was higher than I thought it should be (I use a Dexcom CGM).  Then I went to my endo and had another A1c done (about 5 weeks later).  It was one full percentage point lower and much more inline with my Dexcom.  The endo's office said they have had this happen with other patients with A1cs done at both of the places with that much or more of a variance.  So how accurate are these tests anyway?  I wonder if they're even worth getting or maybe I should just go off my Dexcom.

Linda
Omnipod Dec 2007
DexCom Seven Plus CGMS Sept 2009
trisha01
Total Posts: 5,987
Topics: 294
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Registered on: ‎10-31-2009

Accuracy of A1c test

Linda,

The A1c is over a period of time. Depending on one's appointment time, that could be 90 days or 120 days. The 120 days is more consistent with the life of the red blood cells. So new ones are being made all the time. That is likely the reason for the difference you have seen. You said that the last A1c, was more consistent, with your Dex. During that 5 week time frame, your Bg's were probably lower, which would help to account for that lower % in A1c. The A1c is just another tool that helps overall. I would say the A1c is very accurate when done with blood draws. Labs make very few mistakes. 

Trisha



Trisha

IDDM (Type 1 Autoimmune) 30+ years ~ Currently using MDI & Minimed CGM ~
Check out my diabetes blog!

  All brittle means, is that one has great fluctuations, which is pretty much hallmark for Type 1's. Some more so than others. - me
  First light brings a new day, new hope, new wisdom, and a chance to start fresh again. - me

If everyone were dealt the same amount of cards, there would be no challenges in life. Challenges are part of life's lessons, to teach us to grow in all aspects, and to learn what we need to learn, to make it in this world. Life was not meant to be fair. -me



~ New Type 1 Info ~ Insulin, Test Strips, Lancets, and Pump Supplies Help ~ Kidney Damage Info ~


Super Advisor
jpg391
Total Posts: 5,032
Registered on: ‎05-22-2011

Accuracy of A1c test

I agree with trisha. Your tests were done five weeks apart and that could lead to two different results in your A1c tests.
James G

I'm just a guy who has had type 2 diabetes for 30+ years.

"It is common sense to take a method and try it. If it fails, admit it frankly and try another. But above all, try something." – Franklin D. Roosevelt

"When you get to the end of your rope, tie a knot and hang on." – Franklin D. Roosevelt

"Happiness is a state of mind." - Walt Disney

"All our dreams can come true – if we have the courage to pursue them". - Walt Disney

Latest A1C 6.0 on 12/11/13

Lipids test on 8/22/13
Total Cholesterol 132
HDL Cholesterol 45
LDL Cholesterol 68
Triglycerides 94

Medications
10mg Simvastain for Cholesterol
500mg Metformin twice a day
10 units Levemir, a long lasting insulin
81mg Asprin once a day
40mg of Quinapril (also known as Accupril) twice a day for HBP
20mg of Lexapro once a day for depression
1mg of Doxazosin once a day at bed time for a Prostate problem
30mg of Buspirone twice a day for Anxiety
Long Lost Member
n3qe-tim
Total Posts: 377
Registered on: ‎11-01-2009

Accuracy of A1c test

Labs still vary substantially with regards to both reference ranges and my particular number for A1C.

e.g. When I went to Labcorp I almost always had an A1C in the 5's and the reference range was like 4.0 to 5.5.

Now when I go to Quest I almost always have an A1C in the low 6's and the reference range is 4.5 to 6.0.

Actually even comparing reference ranges between the two labs is hard because they tag it up with all kinds of extra text.

My conclusion is that A1C can easily vary +/- 1% between different labs. I am very very critical of the thought of "equating" an A1C with an average bg from a simple universal table, as a result. It's way more complicated. And that's way before we get into individuals that are "high glycators" vs "low glycators".
trisha01
Total Posts: 5,987
Topics: 294
High Fives: 567
Blog Posts: 59
Solutions: 69
Registered on: ‎10-31-2009

Accuracy of A1c test

Good point, Tim. I keep forgetting that labs differ in ref ranges, etc.

Trisha



Trisha

IDDM (Type 1 Autoimmune) 30+ years ~ Currently using MDI & Minimed CGM ~
Check out my diabetes blog!

  All brittle means, is that one has great fluctuations, which is pretty much hallmark for Type 1's. Some more so than others. - me
  First light brings a new day, new hope, new wisdom, and a chance to start fresh again. - me

If everyone were dealt the same amount of cards, there would be no challenges in life. Challenges are part of life's lessons, to teach us to grow in all aspects, and to learn what we need to learn, to make it in this world. Life was not meant to be fair. -me



~ New Type 1 Info ~ Insulin, Test Strips, Lancets, and Pump Supplies Help ~ Kidney Damage Info ~


Super Advisor
Pam01
Total Posts: 2,066
Registered on: ‎11-02-2009

Accuracy of A1c test

I think there's an interesting question in "is it worth getting an A1C?" - For the majority of the diabetic population, it gives a more accurate overall view of management than sporadic meter testing done by many diabetics.

For those who find their way to this board, who are looking for tighter control and testing upwards of 10x/day - I wonder about the "necessity"??

I like it because my dad (T2), myself (T1 on pump) and my husband (still holding on the tail end of a working pancreas transplant done 15 years ago) can "compare" with a single number!!
Pam

Diagnosed Type 1 at age 16 months, over 45 years now
Minimed pump and cgm since July '09. Metformin (insulin resistance), levothyroxine(thyroid), losartan (BP)

I have traveled cross country, and to Canada, UK, Kenya, Mexico, Jamaica, Equador/Galapagos islands, and lived in Egypt for a year.
trisha01
Total Posts: 5,987
Topics: 294
High Fives: 567
Blog Posts: 59
Solutions: 69
Registered on: ‎10-31-2009

Accuracy of A1c test

Bumping to see if my reply to you shows up. It did in the right hand column, but not here. It figures, it is the weekend.

Never mind.... I put this one in the wrong thread! Oopsy!  

Trisha



Trisha

IDDM (Type 1 Autoimmune) 30+ years ~ Currently using MDI & Minimed CGM ~
Check out my diabetes blog!

  All brittle means, is that one has great fluctuations, which is pretty much hallmark for Type 1's. Some more so than others. - me
  First light brings a new day, new hope, new wisdom, and a chance to start fresh again. - me

If everyone were dealt the same amount of cards, there would be no challenges in life. Challenges are part of life's lessons, to teach us to grow in all aspects, and to learn what we need to learn, to make it in this world. Life was not meant to be fair. -me



~ New Type 1 Info ~ Insulin, Test Strips, Lancets, and Pump Supplies Help ~ Kidney Damage Info ~


Advisor
4xgrandma
Total Posts: 85
Registered on: ‎11-04-2009

Accuracy of A1c test

But the one point I was trying to make was not the difference between the 2 A1cs - I realize the time difference of 5 weeks can make a big difference.  I'm talking about the difference between the A1c and my Dexcom info.  The first test was vastly different than the Dexcom and the second was more inline with the Dexcom.

Linda
Omnipod Dec 2007
DexCom Seven Plus CGMS Sept 2009
trisha01
Total Posts: 5,987
Topics: 294
High Fives: 567
Blog Posts: 59
Solutions: 69
Registered on: ‎10-31-2009

Accuracy of A1c test

Linda,

I think that what I wrote, which is copied and pasted just below, covers that. I will highlite the part that would be specific to it.

I wrote:
"You said that the last A1c, was more consistent, with your Dex. During that 5 week time frame, your Bg's were probably lower, which would help to account for that lower % in A1c."

Question for you....does the Dex show an A1c? Or are you going by the S.D.?, or ??????

Trisha



Trisha

IDDM (Type 1 Autoimmune) 30+ years ~ Currently using MDI & Minimed CGM ~
Check out my diabetes blog!

  All brittle means, is that one has great fluctuations, which is pretty much hallmark for Type 1's. Some more so than others. - me
  First light brings a new day, new hope, new wisdom, and a chance to start fresh again. - me

If everyone were dealt the same amount of cards, there would be no challenges in life. Challenges are part of life's lessons, to teach us to grow in all aspects, and to learn what we need to learn, to make it in this world. Life was not meant to be fair. -me



~ New Type 1 Info ~ Insulin, Test Strips, Lancets, and Pump Supplies Help ~ Kidney Damage Info ~


Super Advisor
Pam01
Total Posts: 2,066
Registered on: ‎11-02-2009

Accuracy of A1c test

Linda - I take what you are asking is that your first A1c was  off compared to your Dexcom average, but (maybe) while your dexcom average stayed about the same, your second A1C was lower AND comparable to your Dexcom??

I think the answer would lie in how accurate  your Dexcom is to your actual BG meter readings??  While my Medtronic cgm is often close but not accurate to BG readings, the average IS about the same over a longer period of time.
Pam

Diagnosed Type 1 at age 16 months, over 45 years now
Minimed pump and cgm since July '09. Metformin (insulin resistance), levothyroxine(thyroid), losartan (BP)

I have traveled cross country, and to Canada, UK, Kenya, Mexico, Jamaica, Equador/Galapagos islands, and lived in Egypt for a year.