Strange Occurrance

I tested myself twice in a row. The first time I didn't get much blood,
but there was enough for the Ascensia Contour to get a reading and not
reject the blood. I received a count of 108mg. I did it again
immediately after trying to get more blood on another finger just to
see if it effected the reading. I got a reading of 100mg on the second
reading. Why would this happen? Either the amount of blood makes a
difference, perhaps which hand makes a difference or the meter simply
isn't accurate? I'm going to try it again on the same hand as the first
reading.

<wipeout64@hotmail.com> wrote in message
news:1163995784.605268.120490@f16g2000cwb.googlegr oups.com...
> I tested myself twice in a row. The first time I didn't get much blood,
> but there was enough for the Ascensia Contour to get a reading and not
> reject the blood. I received a count of 108mg. I did it again
> immediately after trying to get more blood on another finger just to
> see if it effected the reading. I got a reading of 100mg on the second
> reading. Why would this happen? Either the amount of blood makes a
> difference, perhaps which hand makes a difference or the meter simply
> isn't accurate? I'm going to try it again on the same hand as the first
> reading.
>


if there isn't enough blood on the test strip it won't read properly ,
it took me weeks to figure out that the blood goes more in the side ,
then it does on the top of the sticks i use

In article <1163995784.605268.120490@f16g2000cwb.googlegroups .com>,
"wipeout64@hotmail.com" <wipeout64@hotmail.com> wrote:

> I tested myself twice in a row. The first time I didn't get much blood,
> but there was enough for the Ascensia Contour to get a reading and not
> reject the blood. I received a count of 108mg. I did it again
> immediately after trying to get more blood on another finger just to
> see if it effected the reading. I got a reading of 100mg on the second
> reading. Why would this happen? Either the amount of blood makes a
> difference, perhaps which hand makes a difference or the meter simply
> isn't accurate? I'm going to try it again on the same hand as the first
> reading.

That's close enough to be within the allowable margin of error. Home
glucometers are allowed to vary as much as 15%. We can't count on them
for exact numbers.

Priscilla

<wipeout64@hotmail.com> wrote in message
news:1163995784.605268.120490@f16g2000cwb.googlegr oups.com...
> I tested myself twice in a row. The first time I didn't get much blood,
> but there was enough for the Ascensia Contour to get a reading and not
> reject the blood. I received a count of 108mg. I did it again
> immediately after trying to get more blood on another finger just to
> see if it effected the reading. I got a reading of 100mg on the second
> reading. Why would this happen? Either the amount of blood makes a
> difference, perhaps which hand makes a difference or the meter simply
> isn't accurate? I'm going to try it again on the same hand as the first
> reading.

Meters are not 100% accurate and your BG changes minute to minute.

--
See my webpage:
http://mysite.verizon.net/juliebove/index.htm

wipeout64@hotmail.com wrote in message
<1163995784.605268.120490@f16g2000cwb.googlegroups .com>...
>I tested myself twice in a row. The first time I didn't get much blood,
>but there was enough for the Ascensia Contour to get a reading and not
>reject the blood. I received a count of 108mg. I did it again
>immediately after trying to get more blood on another finger just to
>see if it effected the reading. I got a reading of 100mg on the second
>reading. Why would this happen? Either the amount of blood makes a
>difference, perhaps which hand makes a difference or the meter simply
>isn't accurate? I'm going to try it again on the same hand as the first
>reading.
>

As far as a home blood testing meter is concerned, you got identical
results. Wait till you try that procedure during a 200 mg/dL blood sugar
episode!

Some additional things to consider when fiddling around like that;

1. A home blood testing meter measures the total sugar in a small sample
of whole blood, then applies a mathematical correction to estimate the
amount of sugar of the plasma fraction of that whole blood sample. That
means it makes some sort of assumption about the number of red blood cells
in that sample.

If you do something to change that number of blood cells from sample to
sample, then the answer will change from sample to sample.

SWAG #1. It could be that squeezing your finger tip, and/or whatever you
did to try to generate enough blood from the first stick filtered out some
red blood cells and produced a sample with more total glucose. (Plasma has
more glucose per unit volume than red blood cells)

2. A home blood testing meter makes some mathematical calculations which
are ultimately based on the exact weight of the blood in the little sample
that was sucked up into the capillary space at the tip of the test strip.

SWAG #2. If you leave a tiny droplet of blood stuck to the end of the
capillary, the meter will try to add some of the glucose in that little
droplet of extra blood to the total amount it measures. Since the meter
doesn't "know" that tiny droplet is there, it will use the wrong "exact
weight" in the calculations and thus generate a higher number.

The CDE at one of my Diabetes Support Group did some fiddling with that
theory and were able to generate consistently higher numbers when they left
a droplet at the end of the strip.

Regards
Old Al

wipeout64@hotmail.com wrote:
> I tested myself twice in a row. The first time I didn't get much blood,
> but there was enough for the Ascensia Contour to get a reading and not
> reject the blood. I received a count of 108mg. I did it again
> immediately after trying to get more blood on another finger just to
> see if it effected the reading. I got a reading of 100mg on the second
> reading. Why would this happen? Either the amount of blood makes a
> difference, perhaps which hand makes a difference or the meter simply
> isn't accurate?

Actually, everything except the third. And a fourth factor: small
amounts of dirt/food/residue on your fingertips can affect the results
too.

Fingerprick blood measurements are not the same as venous blood glucose
measurements. Two different fingerpricks (or even the same fingerprick
at different times, I was once taught to wipe off the first drop of
blood and use the second) will get different samples of blood. There is
extensive literature on this subject to be found by google.

Hint about your misuse of the word "accurate": the best research papers
call ALL such measurements (fingerprick, venous, whatever)
"estimations". Nobody has the right answer.

Tim.

On Sun, 19 Nov 2006 20:09:44 -0800, wipeout64@hotmail.com wrote:

> I tested myself twice in a row. The first time I didn't get much blood,
> but there was enough for the Ascensia Contour to get a reading and not
> reject the blood. I received a count of 108mg. I did it again
> immediately after trying to get more blood on another finger just to
> see if it effected the reading. I got a reading of 100mg on the second
> reading. Why would this happen? Either the amount of blood makes a
> difference, perhaps which hand makes a difference or the meter simply
> isn't accurate? I'm going to try it again on the same hand as the first
> reading.

If the true reading was 104, these are +-4% - this is really very good.
Those are essentially the same. FDA guidelines for glucose meters indicate
an accuracy of +-20%. If you'll look at the numbers on your 'control
solution' or 'test solution' or whatever they call it, you can ascertain
that the manufacturer readily accepts +-15% - the difference of your
readings is well within that margin. I rarely see two consecutive readings
that close - I recheck whenever I see a number I was not expecting -
either higher or lower. Seldom do I see two readings within 10%. BTW I
have the same meter, and it does seem to be better than others. After a
year and a half, the only factor I've been able to determine may have much
effect is the room temperature - I've not been able to nail it down, but
it does seem that readings are higher in a cooler area, and I think the
changing temp may affect readings as well - all the instructions say is
that equipment should be "room temperature".

Wow! Thanks for all these facts. I realized that these meters were not
necessarily accurate, but I assumed they were all stable, which is not
the case.


wipeout64@hotmail.com wrote:
> I tested myself twice in a row. The first time I didn't get much blood,
> but there was enough for the Ascensia Contour to get a reading and not
> reject the blood. I received a count of 108mg. I did it again
> immediately after trying to get more blood on another finger just to
> see if it effected the reading. I got a reading of 100mg on the second
> reading. Why would this happen? Either the amount of blood makes a
> difference, perhaps which hand makes a difference or the meter simply
> isn't accurate? I'm going to try it again on the same hand as the first
> reading.

not accurate? not stable? maybe get a better meter!
My OneTouch Ultra is never more then +/- 5pt from
what my vein draw from LabCorp takes for my A1C
when I use the same drop that they use. I'd say the
meter is VERY accurate and VERY stable.

--
Reisa, T1, Animas IR1250 Pumper
DX-5/00 ASD-7/00
A1C: 6.2% (8/24/06)
Daily CHO: 150-200gm
TDD: 34-38u
<wipeout64@hotmail.com> wrote in message
news:1164049715.943089.159070@j44g2000cwa.googlegr oups.com...
:
: Wow! Thanks for all these facts. I realized that these meters were not
: necessarily accurate, but I assumed they were all stable, which is not
: the case.
:
:
: wipeout64@hotmail.com wrote:
: > I tested myself twice in a row. The first time I didn't get much blood,
: > but there was enough for the Ascensia Contour to get a reading and not
: > reject the blood. I received a count of 108mg. I did it again
: > immediately after trying to get more blood on another finger just to
: > see if it effected the reading. I got a reading of 100mg on the second
: > reading. Why would this happen? Either the amount of blood makes a
: > difference, perhaps which hand makes a difference or the meter simply
: > isn't accurate? I'm going to try it again on the same hand as the first
: > reading.
:

According to the data sheets for the AccuCheck Comfort Curve strips,
the "CV" is 3.2 which has been explained to me as meaning that
one standard deviation is 3.2%

"Standard deviation" is defined as being the amount of deviation
from average that is equal to or greater than the deviation of half
of the samples.

So if the "correct" reading is 100, half of the strips will read
between 97 and 103.

Three standard deviations encompasses about 98%. So 980 of a thousand
strips will read between 90 and 110.

If this intrigues you and you want to know more, find a math junkie
and ask him or her for all the gory details of Gaussian distribution,
variance, standard deviation, etc.

--
Wes Groleau

You're all individuals!
Yes, we're all individuals!
You're all different!
Yes, we are all different!
I'm not!

("Life of Brian")