Blood sample size - significant?

Bluetit1802 said:

It is hard enough to get one drop, never mind a second.

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I am the opposite I bleed very easily, in fact people often say I am an annoying bleeder.

Mr_Pot said:

I am the opposite I bleed very easily, in fact people often say I am an annoying bleeder.

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The only time I bled when finger pricked, and bled profusely, was when I'd had 2 days' worth of blood thinning injections in hospital! It was all over the bed sheets. I think they overdosed me, but whatever, they stopped the injections.

No blood glucose measuring system is accurate.

Whether it's a home meter or hospital system, they're not weighing a physical thing in absolute terms, like you might do weighing some lamb chops on a precision set of scales.

They're all just inferring (which is a polite way of saying "guessing') what bg might be from a tiny electric current created by glucose oxidase and then a redox action started by breaking down glucose into what must surely turn up as a pub quiz answer sometime soon - hydrogen peroxide and d-glucono 1.5 lactone.

They're all measuring ghosts, little flitters of electrons, which are then run through an algorithm of the maker's choosing.

Does this mean we can't rely on them? No, we can. But we have to accept that what is produced is, at best, a close approximation to the truth.

That's why I think that fretting about fractional, or even, in some cases, integer, differences, doesn't really matter that much.

It said 5.1 and then it said 6.4? Leaving aside obvious explanations (like, erm, bg moves all the time - it's a highway, not a static system), those numbers are basically the same - they are both in range.

It troubles me a bit, but not much, that people fret about fractional differences. We have modern meters/cgm, so we pay attention to decimal points.

Do they actually matter? I would say not: meters are not accurate but near enough; anything after the dot is pointless; being generally in range is good enough without getting squirelly about fractions.

I've put a link below to a seller of glucoflex-r colour changing strips. I used that sort of thing for a few years after dx 30 yrs ago, and bought some on a nostalgia trip a few months ago.

Using those, (I learned a lot about incredibly subtle differences in colour), my main focus was am I generally in a 4 to 7 range or out of it?

Decimal points played no part in answering that simple question. But now that we're all teched up with bluetooth enabled meters, cgm etc. etc. , we seem to focus on and criticise every slight inconsistency.

Are we losing sight of the fact that bg measurent is really difficult and being "near enough" is good enough?


https://www.betachek.com/uk/gfx?___store=uk_default

Scott-C said:

Are we losing sight of the fact that bg measurent is really difficult and being "near enough" is good enough?

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I am a fan of the "near enough is good / close enough" measuring system on my bgl's.

LittleGreyCat said:

@Scott-C
Decimal points? The difference between 5.1 and 6.4 is considerably more than a decimal point. the reading is over 25% higher. Being dismissive undermines your argument.

Normal blood sugar ranges are allegedly "4.0 to 6.0 mmol/L (72 to 108 mg/dL) when fasting" so anything above 6.0 for a fasting reading (which this was) is potentially significant.

I agree that the difference between, say, 8.9 and 9.1 (or even 5.9 and 6.1) is not that significant. However when you get into the lower end of the range the whole numbers (not decimal points) can be quite significant.

Consider a reading of 4.0 and one 25% lower. The 3.0 reading is in hypo territory and should be cause for immediate concern. So a 25% difference can be quite significant.

Meters are only approximate and it is best to stick to one meter because you learn what the readings mean to you. However discrepancies above a certain percentage do raise questions.

Having said all that, the link https://www.diabetes.co.uk/blood-glucose-meters/blood-glucose-meter-accuracy.html gives quite a large range for acceptable accuracy for meters. For example a meter would still be regarded as acceptable if it gave a reading of 5.0 for a real value between 4.0 and 6.25. However I would not expect that any meter would push the boundaries of acceptable accuracy. I would expect that there would be some difference between meters from different manufacturers but not massive differences.

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Sorry if you took my post the wrong way, LGC. Things said in text often don't come across the same way as they would when said face to face.

I was trying to open the conversation out a bit into the basic truth, in my view at least, that bg measurement is surrounded by a haze of uncertainty, and it's up to each of us to use the tools available to us to make best guesses about what to do next.

LittleGreyCat said:

Darn and poot!

Clicked on "funny" and I meant to click on "agree".

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I have put you on my list!

LittleGreyCat said:

Decimal points? The difference between 5.1 and 6.4 is considerably more than a decimal point.

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Yes, but the 5.1 was at 10:30, the 6.4 was at 13:10.

Sure, if you'd got that difference from testing on your meter just before the hospital sample was taken, you might have a point.

But there was a two hour forty minutes gap between the two. Why would you expect them to be the same over that range of time?

Bg is a constantly moving target. It moves around by more than those margins in non-Ts, so it's no surprise at all that there will be variances in Ts.

Comparing a settled fasting bg to one several hours later, which will be influenced by moving about and the slight adrenalin rush which often accompanies a hospital visit, is not a valid comparison.

Scott-C said:

They're all measuring ghosts, little flitters of electrons, which are then run through an algorithm of the maker's choosing.

Does this mean we can't rely on them? No, we can. But we have to accept that what is produced is, at best, a close approximation to the truth.

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You've just made my day: I rather like the idea that I'm measuring bloody little ghosties, who pop out when I prick my finger to tell my meter whether or noi I've been feeding then correctly.... Though at times I am actually prone to believe that some of them might just be lying little sods...

But seriously, I've always been more than happy that my meter is at least mainly consistent in the patterns it shows me , even through my glucose is in a constant state of flux And if it throws the occasional high or low wobbly, it's then up to me to try to find what may have happened to cause me (usually!) to malfunction.

Robbity