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Re: [IP] Re: Glucose meters ...arrcchhhgggh!

At 08:57 AM 10/24/2001, you wrote:
>Okay, folks, I need some of your expert input on this.
>What's the deal with different brands of glucose meters giving very
>disparate readings within seconds of each other?  I've been using a One
>Touch Basic (is that outdated already?) but wanted another meter to keep at
>work so I wouldn't have to keep lugging the same one around.  So I grabbed
>an AtLast metering system (a sample) from my doctor's office and ordered
>gobs of lancets and strips to use with it.
>Trouble is, I get different readings from the two meters, when one sample
>is taken directly after the other!  And I mean 12-15 points difference!
>What's the deal here?  I did read somewhere that the AtLast system, which
>uses samples from the forearm, is only good for fasting bgs, but all I've
>done have been fasting, and still there is a significant discrepancy.  Can
>anyone help explain this?
>Thanks so much,

First of all, I am a user, not an expert. There are several issues that 
could account for that level of difference.

1, Home test meters are designed/constructed and tested to give reading 
with an allowable error up to 20%. Your 12-15 points is within this limit.

2. The One Touch Basic is calibrated to give readings as the concentration 
of glucose in whole blood (the total sample) while I believe (??) the 
AtLast is calibrated to read glucose concentration in blood plasm. 
Typically for the same sample a meter calibrated for whole blood will read 
about 12% lower than one calibrated for plasma. This is normal and simply 
reflects the fact that all the free glucose is in the plasma which is a 
slightly smaller volume than the whole blood.

3.  Finger stick samples and forearm sample can give statistically 
different results. This is particularly true if the glucose level is 
changing rapidly. The forearm results tends to lag slightly behind that of 
the finger. This is documented in a report available from TheraSense 

The recommendation I have heard many times is that if you use more than one 
meter they should be the same brand/model using the same type test strips 
(preferably the same lot of strips if possible). I also avoid switching 
from finger to arm and do all of my test with samples from the forearm.

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