Finger prick variation

[louisew]

Seriously, washed hands, took a finger prick on right hand . Reads as 4. Left hand 5????. Repeat right hand, 4 again, left 5! Cgm reading which is nearly always usually 1 mmol higher is reading as 4. I’m going to assume it’s 4. Sometimes there’s a 2 mmol difference between hands, and as I have tight control, I’ll assume it’s the lower one. It would be nice to be able to rely on the finger pricks at least. A 20% variation seems a lot

 

[John Gray]

Is there any significant difference between your two hands - apart from their mirror-image-ness of course!
Maybe your 'dominant hand' is your right hand, and the blood flow therein is (say) 20% better than in your left hand?

Rather more seriously, are not the results, as in the mantra of school physics lessons, "within the bounds of experimental error"...

 

[Docb]

Remember this?

Thread 'What's in a number?'

Mar 8, 2021

We have a lot of members, particularly those new to testing, asking about blood test results and what they mean or what is a "good" number. As many of you are aware I like numbers, mostly because they are what they are and do not have any opinion.

This morning, I woke up, got out of bed, did a finger prick and got a 4.3. Checked another finger and got a 4.2. Tried a third finger and got a 5.1. This led to me doing something I have wanted to do for a while and this was to take 10 consecutive tests on different fingers and both thumbs to see what the variation was. The next seven...

• Docb
• Replies: 6
• Forum: General Message Board

• 

Variations of +/- 1 about the mean of a set of results taken at or about the same time is what is to be expected. I would not worry about which hand, you would get the same variation if you did enough tests on one hand. The results you are getting are to be expected and reflect the precision the instrument is capable of.

And another bete noir of mine - percentages. The difference is not 20% it is a difference of 1 unit. It is only 20% because the numbers are low.

As I keep on saying, the hand held blood glucose meter is an amazing bit of kit but like any measuring device you have to work within its limitations.

 

[louisew]

Is there any significant difference between your two hands - apart from their mirror-image-ness of course!
Maybe your 'dominant hand' is your right hand, and the blood flow therein is (say) 20% better than in your left hand?

Rather more seriously, are not the results, as in the mantra of school physics lessons, "within the bounds of experimental error"...

I am right handed but apart from writing, use them both equally.

 

[Martin.A]

Seriously, washed hands, took a finger prick on right hand . Reads as 4. Left hand 5????. Repeat right hand, 4 again, left 5! Cgm reading which is nearly always usually 1 mmol higher is reading as 4. I’m going to assume it’s 4. Sometimes there’s a 2 mmol difference between hands, and as I have tight control, I’ll assume it’s the lower one. It would be nice to be able to rely on the finger pricks at least. A 20% variation seems a lot

You could test all six fingers and get six different results. I've long given up trying to figure out why. After all these years I know what my usual range is so if I get what for me is an out-of-range reading I'll switch hands and do a second test, and as long as there's no huge difference I'll average the two.

 

[Leadinglights]

I think there is only mileage in retesting if you are suspicious that a reading is out of step with what you expect otherwise you will be wasting strips and not gaining any useful information.

 

[Lucyr]

Seriously, washed hands, took a finger prick on right hand . Reads as 4. Left hand 5????. Repeat right hand, 4 again, left 5! Cgm reading which is nearly always usually 1 mmol higher is reading as 4. I’m going to assume it’s 4.

What a waste of test strips. None of the readings are that accurate so can’t expect them to be the same. If you feel low or are going to be active have a small snack, you don’t need to waste 4 test strips on deciding that

 

[debs248]

If I get a result that feels "wrong", I'll test again on another finger, ideally on the other hand. Sometimes they're near identical, I think the largest variation I've had was 12.2 v. 10.8.

Short of testing yet again, I don't know for certain whether it was the finger or test strip that was "dodgy". I certainly wouldn't test more than twice as I don't think I'd get any more useful info.

 

[harbottle]

Loads of factors that make glucometers vary from a lab result. For a start, they measure blood from capillaries whereas the labs use venal blood. (Capillary blood is 'before' glucose has been used by muscles, so the readings can be higher.)

Temperature & environment can affect the strips (They are just an enzyme that reacts to the glucose in blood). As can dehydration & triglyceride levels.

Different manufacturers will have different algorithms to work out the value from the tiny electrical current & perhaps temperature - cold temperatures will mean slower reactions so the device will try to compensate for that. The sample size can also affect accuracy.

I found with dong some tests on my own fingers that my Contour Next is incredibly consistent. The same can't be said for other devices I tried. I got mine for free, but it's more expensive than other models to buy and the strips are not cheap. Which is why I use Contour Blue instead!

 

[Docb]

@harbottle, Like all measuring kit, you have got to decide whether it is good enough to make sound decisions based on the number it gives and the answer is a resounding yes for the glucometer. All sorts of things will affect the numbers on the screen but they can be used with confidence provided to you not try too be too cute with their interpretation.

A parallel might be the printed rollup tape measure you see hanging round a tailors neck. Perfectly adequate for making a nice fitting suit - just don't try and use it to build an engine.