Diabetes testing

[Elizabeth I]

Apologies if this has been answered - I did run a search and found a diabetes thread but it didn't seem to cover this question.

I keep seeing ads for diabetes blood test meters that allow you to obtain the sample from the arm or some area of the body other than a fingertip. Why is/was blood from the fingertip preferred for these tests? Why couldn't blood from the arm, or the thigh, or for that matter, the foot, give an accurate reading? Isn't blood blood?

Thank you.

 

[Emet]

From Wiki (FWIW):

Alternative site testing: Smaller drop volumes have enabled "alternate site testing" — pricking the forearms or other less sensitive areas instead of the fingertips. Although less uncomfortable, readings obtained from forearm blood lag behind fingertip blood in reflecting rapidly changing glucose levels in the rest of the body.

http://en.wikipedia.org/wiki/Glucose_meter



Another source (I think they manufacture glucose meters):

When Is Testing On The Finger Preferred?

It is important to note that when your glucose is changing rapidly, there may be a difference in the glucose readings between your finger and other test sites, like the forearm, upper arm, thigh, calf, and other areas of the hand. Because blood flow to the finger is three to five times faster than other alternate sites, blood samples from the finger may show changes in your glucose sooner than the forearm, upper arm, thigh, calf, and other parts of the hand. The possible difference in glucose readings between the finger and other alternate sites could delay your detection of hypoglycemia. Vigorous rubbing of the alternate test sites before lancing will help to minimize the difference between finger and other alternate site test results.3

http://www.abbottdiabetescare.com/alternate-site-testing-with-freestyle-systems.html

IANAD

 

[Agular]

Yes, but how long of a delay?

 

[casebro]

Yeah, how fast can it possibly be rising or dropping?

I've got a meter that would take about ten seconds per reading. But what could I eat that would raise t fast enough to show a difference between sites? Or when would I need to eat it?

Basically, I tend to think that there is no practical difference, but a theoretical one, and in this litigious society, they better cover their butts.

That all said, while my meter is good fro alternate sites, I only tried it once. You need to do a spot that is firm enough for the spear to poke a hole in the skin. Over bones don't count. So I do fingertips.

 

[aofl]

So I do fingertips.

I hope you do the sides of the fingertips instead of the pads.

I only use the sides of my pinky fingers and avoid a lot of pain that way.

A

 

[littleroundman]

While under "normal" blood glucose conditions, the differences are not great in readings taken from fingertips and the alternative sites,

however, during periods of rapid BG drops, i.e. an approaching state of hypoglycemia, the lag time between fingertip and alternative site glucometer readings can vary between 5 and 20 minutes: http://www.liebertonline.com/doi/abs/10.1089%2F15209150152607141

 

[Beerina]

From Wiki (FWIW):

Alternative site testing: Smaller drop volumes have enabled "alternate site testing" — pricking the forearms or other less sensitive areas instead of the fingertips. Although less uncomfortable, readings obtained from forearm blood lag behind fingertip blood in reflecting rapidly changing glucose levels in the rest of the body.

http://en.wikipedia.org/wiki/Glucose_meter



Another source (I think they manufacture glucose meters):

When Is Testing On The Finger Preferred?

It is important to note that when your glucose is changing rapidly, there may be a difference in the glucose readings between your finger and other test sites, like the forearm, upper arm, thigh, calf, and other areas of the hand. Because blood flow to the finger is three to five times faster than other alternate sites, blood samples from the finger may show changes in your glucose sooner than the forearm, upper arm, thigh, calf, and other parts of the hand. The possible difference in glucose readings between the finger and other alternate sites could delay your detection of hypoglycemia. Vigorous rubbing of the alternate test sites before lancing will help to minimize the difference between finger and other alternate site test results.3

http://www.abbottdiabetescare.com/alternate-site-testing-with-freestyle-systems.html

IANAD

I wonder if that's a rationalization. In science class in 7th grade long, long ago, we used lancets to take blood samples to do our blood types. We did them on the fingertips because that's the one place that doesn't scar.

 

[littleroundman]

Not at all.

While hypoglycemic reactions in type 2 diabetics are far less common, hypoglycemic reactions in type 1 diabetics are of particular concern and potentially even fatal.

Even a 5 minute difference in returning an accurate BSL is unacceptable, thus the necessity for fingertip testing.

 

[anor277]

Not at all.

While hypoglycemic reactions in type 2 diabetics are far less common, hypoglycemic reactions in type 1 diabetics are of particular concern and potentially even fatal.

Even a 5 minute difference in returning an accurate BSL is unacceptable, thus the necessity for fingertip testing.

If it (a hypoglycaemic bout) has reached that stage, the priority is to consume some form of sugar not test your or the patient's blood glucose. Accurate (home) blood sugar testing has only been around for the last 20 years or so, and while it is extremely useful it won't do anything for hypoglycaemia except tell you that you have it (and when your sweating buckets and away with the fairies, DUUUUUUUH).

 

[littleroundman]

If it (a hypoglycaemic bout) has reached that stage, the priority is to consume some form of sugar not test your or the patient's blood glucose. Accurate (home) blood sugar testing has only been around for the last 20 years or so, and while it is extremely useful it won't do anything for hypoglycaemia except tell you that you have it (and when your sweating buckets and away with the fairies, DUUUUUUUH).

That's not true in all cases.

Many/most long term insulin dependent diabetics can "usually" sense when their BSL is dropping rapidly.

"Usually" but not always, and the "feeling" is easily misinterpreted, ESPECIALLY when a new treatment regime has been introduced and/or type of insulin changed.

For example, I know of patients (including an MD, BTW) who died following being switched from porcine/bovine insulin to the newer biosynthetic insulin/s because they failed to recognize the differing early warning signs of hypoglycemic reaction in the biosynthetic product.

IOW, the it is entirely possible to "feel" as if a hypo is imminent, when, in fact, the "feeling" has an entirely different causation.

Any suspicion needs to be verified, and quickly.

In such circumstances, even a 5 minute delay in obtaining results can be extremely dangerous, if not fatal.

"Assuming" a hypo is taking place and acting accordingly can be equally as dangerous.

The same applies to a lesser extent to those with type 2 diabetes.

Medication changes and unusual energy consuming activities can cause rapid hypos, particularly in those in the early stages of treatment/s which includes medication and who haven't become savvy with the condition and/or the effects of medication/s.

 

[casebro]

The sweating is not caused by low sugar, but by DROPPING sugar. Depends on how high you started....

And most insulin users ARE type two. Due to insulin resistance, they may take 200-300 units per day. Too much exercise lowers the resistance, and BAM, hypo.

You don't need to ask me how I know, do you?

 

[Fnord]

It's an odd thought, but doesn't arterial blood get to the bicep or forearm before it gets to the fingers?

Or was that one of the days that I skipped Human Pysiology class?

 

[Skeptic Ginger]

This is kind of repeating what's been said:

Your fingers hurt even if you use the sides. Older testing devices needed a bigger drop of blood not as easily obtained from the forearm. The newer models have a wick action on the test strip and use less blood. The forearm is much less painful area of skin to pole holes in for the blood sample.

 

[Skeptic Ginger]

It's an odd thought, but doesn't arterial blood get to the bicep or forearm before it gets to the fingers?

Or was that one of the days that I skipped Human Pysiology class?

You probably just didn't recall the details.

All arterial blood is headed out to the tissues. It reaches the capillaries where the wall is thin enough for O2 exchange. From there on the blood is in a vein headed back to the heart and lungs.

All the blood we obtain by finger or forearm sticks is coming from capillaries. Arterioles and venules are deeper than the lancet blade.


The bloodstream pressure system tells you the blood couldn't be dumping O2 in the upper arm then going on to dump more O2 further down the arm. Once the blood passes the capillaries, the amount of pressure from the heart pump is negligible. The blood vessels get smaller and smaller until you reach the capillaries. From there on the vessels get bigger. The blood pressure from the heart is pretty much dissipated beyond the capillaries as the diameter of the veins are larger now than the last place the blood was, the capillaries. So it wouldn't be efficient for the blood to move on supplying O2 to more and more tissues.

 

[littleroundman]

And most insulin users ARE type two. Due to insulin resistance, they may take 200-300 units per day. Too much exercise lowers the resistance, and BAM, hypo.

My bad, I should have specified "injectable insulin" users.

That could have then lead to explaining how and why a hypoglycemic reaction differs between users of rapid acting/short acting/intermediate acting/long acting injectable insulin and the possibilities involved in the oral insulin usage you point out.

Hopefully, this thread remains as a generalized discussion and not as a source of self diagnosis and/or treatment for readers.

 

[Skeptic Ginger]

The sweating is not caused by low sugar, but by DROPPING sugar. Depends on how high you started....

And most insulin users ARE type two. Due to insulin resistance, they may take 200-300 units per day. Too much exercise lowers the resistance, and BAM, hypo.

You don't need to ask me how I know, do you?

While no doubt some diabetics may use a lot of insulin, I think that high of a dose is pretty rare.

 

[Loss Leader]

I keep seeing ads for diabetes blood test meters that allow you to obtain the sample from the arm or some area of the body other than a fingertip. Why is/was blood from the fingertip preferred for these tests? Why couldn't blood from the arm, or the thigh, or for that matter, the foot, give an accurate reading? Isn't blood blood?

This is actually an easier question than a lot of people on the thread are making it out to be.

Meters that advertise that you can use alternate testing sites are really advertising that they use a smaller blood sample than older models. Your fingers bleed a lot more readily than alternate sites. So, a machine that can get a reading from 0.3 whatevergrams of blood can use a site that doesn't bleed very well. An old machine that needs 1.0 whatevergrams really needs a finger.

But, these ads are lying to you in one very important way - it's not the glucometer that's most important for alternate test sites, it's the lancing device. A good lancing device can get you a great sample from any alternate site. I use the Ascencia Contour because my doctor gave it to me free. But I threw away the lancet that came with it and picked up an Acucheck Multiclick: 6 lancets in a drum, far less fumbling, good depth guage = less time spent doing that.

Incidentally, when I've bothered to take my blood from my forearm and my finger, I notice that my finger blood sugar is usually 10 points lower (American system).

 

[littleroundman]

This is actually an easier question than a lot of people on the thread are making it out to be.

What would make it "easier" is if the OP and subsequent posters specified whether the "diabetes" to which they are referring is type 1, type 2 or another type of "diabetes"

They are similar but not the same in all regards, including the relevance/importance/method of self monitoring.

 

[Skeptic Ginger]

...
Incidentally, when I've bothered to take my blood from my forearm and my finger, I notice that my finger blood sugar is usually 10 points lower (American system).

I suggest your sample size may be giving you skewed results.

Edited after looking for a physiological reason test site would differ:

Keep in Mind That Results May Vary

It is important to know that blood sugar results can vary depending on when and where you test your blood. For example, if you get a sample of blood from a testing site on your thigh and your blood sugar is going up significantly at the time, you may get a delayed result. In other words, the result you receive may be what your blood sugar was 20 to 30 minutes ago but it is not accurate for the present moment. You might be able to speed up the process slightly by rubbing the area until it is warm to increase blood flow to that site.

So the blood sugar would be pretty uniform in the blood stream. This site is claiming circulation might be exchanging at different rates at the capillary level different body sites. That would probably be true if you had venous insufficiency and were testing a dependent peripheral site, especially the feet. But I question just how different circulation is between the forearm, thigh and hand. I am willing to agree if I find more about why the rate would differ by that much short of sites with obviously sluggish circulation. One would expect then to see the glucose reading higher in your forearm than your fingers after a meal and lower before a meal if one was getting a result based on the blood exchange differing in each site.

In other words if the discrepancy was due to delayed turnover of refreshed blood, then one site wouldn't be lower, it would represent your blood sugar at a different time.

 

[Skeptic Ginger]

What would make it "easier" is if the OP and subsequent posters specified whether the "diabetes" to which they are referring is type 1, type 2 or another type of "diabetes"

They are similar but not the same in all regards, including the relevance/importance/method of self monitoring.

But the question is about blood sugar testing.