Been a while since anyone posted to this discussion. I've been type 2 for almost 3 months. Read somewhere that test results can vary +- 20 points. I checked out yesterday and today. Sure enough, if I tested twice or even three times the numbers varied by 10 points. Since I'm aiming to stay under 110 and trying to see relationships to food I eat and monitor 2 hours out, I'm not sure now how accurate anything is.
Does it matter?
Any other meter that might be more accurate. Last comment here was in 2007 which was 5-6 years ago.
Well, we hear that meters are only accurate to +/- 20%, but I think in use, you can reasonably expect them to be more accurate. My experiences with meters is that while all meters might be +/- 20%, my meters don't have that much variation. I test with my meter at the same time as my lab draw and they are much closer than 20%, generally within 5%. And then if I take a bunch of tests repeatedly at the same time, I get agreement within about 5-10%. So the test to test repeatability is pretty good.
And the most important thing to remember is that meter errors comes from two sources, an error in the average and an error from the variation. My experience is that much of the error is probably just variation and most meters are probably on average much metter than the 20% number, at least 10% if not better. So I look for averages and place less emphasis on any single number.
If you are not dosing insulin your meter being off 20% to 30% from time to time should not be a big
concern...JMHO
I have seen large discrepancy's in my meter results and what my actual BG is at that time. Yes
they can be off more than 20% on one test but most results are much closer. After some time you
will probably notice and suspect your meter is displaying a inaccurate result. Many people that use
bolus insulin and or do corrections will re-test if they suspect a bogus meter reading. I always retest
if my meter result does not fit my normal pattern or there is a big diffrence when compaired to my
CGMS.
It's best to always wash and make sure your hands are thoroughly dry before your test. Contamination can cause high readings and just a small amount of moisture will dilute the sample causing a false lower than actual BG reading. Try to always do your test
the same way including the position you hold the test strip and apply the sample.
Your blood is made up of liquid and solids and some segregation occurs when the
sample is drawn into the test strip. This segregation can be different if the test strip
is pointing at the celling when compared to pointing it at the floor when applying the
The test I run on all my meters that I compare to the BG I get from my blood draw every three months really aren't that much different from each other or the blood draw. Certainly within 20%, usually within 10%, and occasionally within 5% of each other and the blood draw.
The +/- 20% really does seem to be the upper limit of the range. I think you can probably do more to affect the accuracy by washing your hands before each test. I know my Accucheck Aviva seems to be super sensitive to any potential contaminated fingersticks while my Freestyle seems to be a lot less sensitive.
Welcome to world of frustration on readings. Personally, my own anecdotal evidence is that my reading depends on drop color (darker is better), whether the strip immediately sucks it up, and the truth is that you can have readings vary right behind each other and using the same source fingerprick.
I do know that if my drop is over about a min old, that I might as well take another sample, because it won't behave right.
The absolute most frustrating things that happen are: watery blood drop (lots of lighter color blood but generally will not wick up right) and a fingerprick that hurts but gives a pinhead droplet.
Different meters? I don't think it makes a great deal of difference myself. Will you do something different if it reads 108 vs 111? Probably not. I have taken on watching the numbers as almost a challenge in itself, but I'm not going crazy about it.
If I'm testing to dose insulin, I will wash my hands and repeat the fingerstick if the first result is far off from my cgm.
For me (and maybe I'm just weird this way I don't know), my right hand fingerstick is always going to be higher than my left hand fingerstick (by 10 points sometimes) so if I repeat a test I do so on the same hand. But maybe that's just me..
