Different Meters with Different Results

boondox · #1 (**permalink**) 03-17-2008, 05:28 AM

This may have been covered before but i haven't seen it so here i go.

I have 2 different meters and they never see eye to eye on the number. I just tried them both on the same finger at the same time and they are 9 points off. Is this normal? Which one do i trust? Since i am pretty much under control at the moment, 9 points isnt a big deal, i dont think, but if i was way high or way low then 9 points could mean something. Unless this is a normal thing then i wont worry about it. Its just confusing.

morrisma · #2 (**permalink**) 03-17-2008, 05:53 AM

Not a surprise at all. Check the meter's manuals or online for accuracy specs. There's a plus/minus tolerance that I'd be willing to bet is greater than 9 points. In fact, I wouldn't be surprised if you used the SAME meter and got a difference of 9 points.
No worries,
Mike

w5wjp · #3 (**permalink**) 03-17-2008, 05:59 AM

The accuracy of meters is only plus or minus 10-15% on a good day. Nine points is no problem.

xMenace · #4 (**permalink**) 03-17-2008, 06:07 AM

Quote:

Originally Posted by w5wjp

The accuracy of meters is only plus or minus 10-15% on a good day. Nine points is no problem.

It is if you aren't in the USA!

morrisma · #5 (**permalink**) 03-17-2008, 06:37 AM

Quote:

Originally Posted by xMenace

It is if you aren't in the USA!

Ok, John 9/18 points is no problem. You know us yanks can't do hard maths.

Mike

Glucoweb · #6 (**permalink**) 03-17-2008, 08:11 AM

It could also depend it the meters use different technology whole vs plasma measuring [from wikipedia: Whole blood glucose vs. plasma glucose: Glucose levels in plasma (one of the components of blood) are generally 10%–15% higher than glucose measurements in whole blood (and even more after eating). This is important because home blood glucose meters measure the glucose in whole blood while most lab tests measure the glucose in plasma. Currently, there are many meters on the market that give results as "plasma equivalent," even though they are measuring whole blood glucose. The plasma equivalent is calculated from the whole blood glucose reading using an equation built into the glucose meter. This allows patients to easily compare their glucose measurements in a lab test and at home. It is important for you and your healthcare provider to know whether your meter gives its results as "whole blood equivalent" or "plasma equivalent."]

I personally cannot stand the +/- 15% error allowed under current laws. But it is better than the currently available alternatives.

solox316 · #7 (**permalink**) 03-17-2008, 03:40 PM

Quote:

Originally Posted by morrisma

In fact, I wouldn't be surprised if you used the SAME meter and got a difference of 9 points.

If only I get get two tests in a row on the same meter with same blood sample to be 9 or fewer points apart! Try like 15 points...

boondox · #8 (**permalink**) 03-17-2008, 04:51 PM

Thanks Everyone! I feel a lot better now. I was hoping it wasn't an issue with one or the other meter.

xMenace · #9 (**permalink**) 03-17-2008, 04:59 PM

I've only had two back to back readings the same ... ever! I've done it a lot.

JRT757 · #10 (**permalink**) 03-19-2008, 08:31 AM

I had a meter that I was having doubts about the readings. During a stay in the hospital for a staph infection, I had my meter brought to me so that I could do comparison readings with the hospital's meter.

My meter was anywhere between 40-50 points HIGHER than the hospital's meter. Their meter was basically the same as a good meter you can buy in a pharmacy. Dr. told me to ditch the meter I had and he wrote a script for a new one for me.

Now if I go to the hospital, I take it with me and am usually only 3-4 points +/- of theirs.

When we did the comparison readings, they got the first drop of blood, I took the second drop from the same finger prick.

Sometimes meters are just bad.

Scrabblechick · #11 (**permalink**) 03-19-2008, 09:03 AM

How about this? Checked my sugar with the meter I generally use. It was 123. Checked with the other meter. 133. OK, 10 points. Not a big deal. Just for giggles and grins, I took the second drop and used the second meter again. 147. Yeah, right. New finger stick, first meter, 122. Also, the meter I generally use was right on the money with what my lab BS was that week. The strips for the other one are too bleeping expensive, in spite of what they say about "accuracy."

Looks like, from what I've read, meter accuracy is wishful thinking more than anything.

fgummett · #12 (**permalink**) 03-19-2008, 09:11 AM

I understood that using a second or subsequent drop can give a misleading reading, especially if you have to massage the finger to produce it...

That said, it is disappointing that home testing is not as accurate as we might like but is 1,000% better than the urine testing which was the only option not that many years ago; and it seems to be accurate enough to provide feedback for those of us taking fast-acting insulin

JediSkipdogg · #13 (**permalink**) 03-19-2008, 01:24 PM

For a small non-scientific test I did here's my results...

Blood Glucose Meter Comparison

I used a large sample of blood and placed it in all the meters and the results were sometimes outstanding.

Scrabblechick · #14 (**permalink**) 03-19-2008, 02:56 PM

What a great self-experiment, Jedi! Thanks so much for re-posting the link, and certainly for ALL your effort! Makes me feel better about my meter.

The moral, I suppose, is find a meter and stick with it. I'm using a True-Track right now, and the first test I did was exactly what my sugar had been at the lab, so I guess that's about as good as it gets. I have and Ultra2, but it consistently reads 10 points higher. Well, sometimes 5 points lower. However, I can actually afford the True Track strips.

I've heard some stuff about the TT meters, but mine has been a consistently good one for me. It's like everything else I'm learning about this disease: everyone is different.