[MadRebel]

Was with my diabetes specialist last week and have been thinking about what he told me. Thus the reason I'm just now posting it here.

Here goes:

We were talking about my meter readings and he said that our actual value is ALWAYS 10% less than what is reflected on our meters. The reason: our meters test the whole blood and the actual a1c test blood plasma which ALWAYS gives a value of 10% less than what our meters say.

So in other words...if I show a meter reading of 5.0, my actual true value is 4.5 (5.0 - 10%), etc, etc.

This is actually kinda worrysome. If I feel I'm getting "down there" say at 3.5 then I'm actually hypo'ing at 3.15.

Is this true? I've been trying to research this on the net but nothing turns up.

Anyone knowledgeable about this?

Take care all

[JediSkipdogg]

It depends on what kind of meter you use and if it reads in whole blood or plasma. Plasma is what all lab tests are pretty much done by. Most meters actually read in whole blood (since we can't seperate the plasma out with a simple fingerstick) and then use the formula and convert the number to plasma results (which is what we see on the screen).

[pinkytricia]

Geeezz...
Well that sucks...

Yes, My Mamí (doctor wanna be) has mentioned that before.... She has called the support line of Freestyle but they told her it might be higher than what it reads.......

How are your A1c ???? Your average meter reading

[JediSkipdogg]

Here's a little more info on the Plasma vs. Whole blood......

"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."

[HelenM]

It depends on the meter but I've checked through all the documentation that came with mine and it doesn't say.

This link gives a list of on the UK market and whether they are plasma or whole blood calibrated,also a graph to show the difference between the two types of readingshttp://www.pasa.doh.gov.uk/evaluatio...ms_leaflet.pdf

It does mean that when people are discussing average BS levels from meter readings onthe forum there may be a 11% difference between them.

[Funnygrl]

Meters tested whole blood like 10 years ago. Any modern meter tests plasma blood.

[nneighbour]

The formula is something like:
HbA1c = (Mean Plasma Glucose mg/dl + 77.3) / 35.6
HbA1c = (Mean Plasma Glucose mmol/l + 4.29) / 1.98
Mean Plasma Glucose mg/dl = (HbA1c x 35.6) - 77.3)
Mean Plasma Glucose mmol/dl = (HbA1c x 1.98) - 4.29

It seems to work out about right to when you use the conversion tables out there.

I'd love to hear from someone who can look back on their 3 month average, and using the formula, see if their HbA1c is similar.

[REDLAN]

I changed over to a new meter just recently - I junked my old one as it was on the edge of it's accuracy when I tested it - interestingly my old one was over-reading so it was kinda self-calibrated to read plasma concentrations anyhow (",)

Anyways I got the new one, and ran the 2 side by side for a bit - my new meter read higher than my old one by about 0.5 mmol - trouble is you never get exactly the same readings from minute to minute or even from the same drop of blood - and I thought the old one was reading high!

for the first couple of weeks this was very frickin annoying as now I got all these high readings, and my average went up by about a 1 mmol (18). I've got my readings back down to where they were, and I have to keep reminding myself that I actually have better control with the same readings - which is a plus I suppose.

the second thing to consider is the meter's stated accuracy...

my ultrasmart strips have a range of 5.9 to 7.9mmol or 107 to 143 mg/dl - it is considered accurate if the meter reads in this range if tested by a control solution.

this means that my meter's accuracy is no better than +/- 1mmol (or 18mg/dl) or about 20%. The good thing is that my meter is very consistent when repeatedly tested with +/- 0.1mmol reading.

the best bit is that you can take it to the clinic and run it side by side with their testing equipment - according to the blurb your meter is considered accurate if it is within 20% of your lab result.

I think personally calibrating a meter to read 11% higher is somewhat of pointless exercise when it's accuracy is around 20% anyway.

[lilituc]

Originally Posted by Funnygrl

Meters tested whole blood like 10 years ago. Any modern meter tests plasma blood.

True...in the US. Not everyone here is in the US, though.