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Sampling errors

D

dreece

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I've been diagnosed as pre-diabetic (initial BG sitting between 6.0 and 6.3 mostly) 4 months ago.

Since then, I've dropped my weight by 60 pounds (and my BMI from around 35 down to 28.8) and test my BG every week with a commercial meter.

It has come down quite a bit, mostly between 4.2 and 4.8, however I do get the occasional, unexplained high reading.

This morning was testing day and it was 6.2 in spite of only modest meals yesterday, together with plenty of exercise. When I immediately tested again (wiped the bllod and got another drop), it was down to a much more reasonable 4.4

On thing I noticed is that after I used the lancet, a pale clear fluid emerged before the blood.

Am I right in thinking that this fluid (plasma, presumably?) mixing with the blood skews the results?

Looking back, I think this has happened a couple of times, but not leading to such a high level as this time. I also seem to need to squeeze my finger quite a bit to get blood out - even when set to maximum penetration.

Any thoughts?

david
 
Try soaking fingers in warm water and pricking the sides of ring fingers because I generally find a better blood flow there.Don't squeeze finger,apply gentle pressure by putting thumb just under when you pricked.If there is clear fluid wipe it away and get fresh drop to come out.
 
Thanks, I followed your advice and tested again this morning and measured a respectable 4.4 again.

I'm still puzzled by the past high readings - is getting high readings when the blood sample is diluted by plasma a known problem? I did find a reference to low hematocrit levels casuing a high BG reading - and plasma diluting the sample would seem to mimic that.

Anyway, at least I know how to do it properly now - I'm due to see my GP in another three months to evaluate my progress (by which time I hope to have dropped my BMI close to 25) and she's going to do a more comprehensive blood test.

dave
 
dreece said:
Anyway, at least I know how to do it properly now - I'm due to see my GP in another three months to evaluate my progress (by which time I hope to have dropped my BMI close to 25) and she's going to do a more comprehensive blood test.

dave
Click to expand...

In the meantime it would be a good plan to do some postprandial testing

http://www.alt-support-diabetes.org/NewlyDiagnosed.htm

in many cases the postprandials go south long before the fasting BG is affected: although many doctors still aren't interested in these numbers you can use them yourself to tune your diet accordingly, and you can always print them out and take them in with you, she might be impressed
 
Thanks, that looks to be a very useful resource.

I just tested a little while ago - perhaps 2 and a quarter hours after my evening meal (a medium-sized indian - no rice.)

Result was 4.7, which to my untutored eye looks OK.

I had lunch about 6 hours previously with my usual 5 mile brisk walk almost exactly half way between lunch and dinner.

Of course, I have no way of knowing what my post-prandial readings would have been a few months back before I lost over 4 stones in weight.

I'll try testing as that site suggests at the one and two hour marks for a couple of days.

I do feel rather heartened by this result, however!

I reckon I can lose another couple of stone or a bit more, that should bring my BMI close to 25 and my waistline down to 36" - 37" - from an original 46" (currently 39"), as I gather that excess flab around the middle is just as big a risk indicator as BMI.

I'm hoping, of course, that having caught it just as I hit marginally pre-diabetic levels, I may be successful in heading off full diabetes for as long as possible as I'm only 57.
 
Thanks, but here's something weird - having tested post-prandial at 4.7 last night, I had a glass or two of diet coke and went to bed.

Got up at 08-30, tested 10 minutes later and measured 5.0 (having been very careful in my measurement technique)

This seems strange, in that I didn't consume any food between the two readings and I'd assumed that diet coke at midnight wouldn't cause any change the following morning - there is obviously something going on here I don't understand!

Any thoughts?

dave
 
Nothing to worry about ,Dave.It's just your body getting ready for the day.Your liver dumps glucose into system ready for energy use during the day.Once you eat your body knows it will have fuel so stops dumping glucose.At a level of 5 you have no worries anyway!! :D
 
Thanks for setting my mind at rest! Now I've read up on the Dawn Phenomenon, and I see that it can affect non-diabetics (and thus, presumably, pre-diabetics) as well as diabetics.

I just did another 2 hour post-prandial and again it was 4.7 (6.1 after an hour), so diet and exercise seems to be working OK.

As Trinkwasser suggested, I think I'll add a weekly post-prandial to my overnight fasting measurement and have the data to hand when I see my GP in 3 months.

At the moment, I'm continuing to average a bit over 2 pounds per week weight loss, so should easily be on target for a BMI of 25 by that time, which she suggested as an initial target (then aim for an eventual target of 10 pounds or so below that, if possible).

I was reading the American diabetes prevention program study results and see that significant (7%-10%) weight loss *may* bring my pre-diabetic glucose levels back to normal. I guess that is why my GP was so enthusiastic about me losing a big chunk of weight.

By the time I hit a BMI of 25, I'll have lost over 25% of my starting weight, so here's hoping!

dave
 
I hope it does take you down to normal levels,Dave but just be aware after that to keep an eye on your weight and dietary intake to keep you at normal levels.
 
It's a circular argument, excess carbs cause excess BG and are (usually) stashed as body fat. Body fat emits inflammatory cytokines which can directly damage pancreatic beta cells and also induce insulin resistance which causes a demand for more insulin to process the glucose, which produces more fat storage.

Anywehere you can break into the cycle is good.
 
Thanks Trinkwasser, that is the most succinct explanation of the problem I've seen.

I am on a pretty low-carb lifestyle and that, together with the exercise ( 5 - 7 miles very brisk walking per day, plus some weight training) is certainly causing my weight to reliably fall - another 3 pounds this last week.

At this rate, I'll be just below a BMI of 25 by Spring.

Did another couple of 2hr post-prandial measurements - 4.7 yesterday lunch and evening, 4.5 after lunch today.

I've only got a limited supply of test strips, enough to do an overnight fast and a pp each week until my GP appointment, so I'll stick to those for now.

dave
 
4.7 is Bernstein's ideal non-diabetic number. I think you've reversed it.
 
I would certainly like to think so!

Measured 4.5 2 hours after eating last night and 4.2 this morning.

I'm guessing that the numbers probably won't go much below those now?

While I found a lot of excellent resources on the web (including here) about managing diabetes, I couldn't find much specifically directed at pre-diabetics, except a generic 'lose weight and exercise more'.

The American DPP study using Metformin or diet/exercise showed interesting results but I don't see much signs of anything similar on this side of the Atlantic.

My GP, while not exactly antagonistic, did seem to be of the 'another fat slob' frame of mind - ok, some justification, but nowhere near as much useful info as I've found here.
 
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