Why Can't Meters Tell Me My Blood Sugar?

Despite new advances in medical technology, those of us with diabetes are still checking our blood sugar levels on glucose meters that are allowed to be anywhere within 20 percent accuracy 95 percent of the time.
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The 72nd American Diabetes Association scientific session took place a few weeks ago.

More than 16,000 medical professionals, scientists, researchers, pharma industry representatives and some well-versed patients attended.

The exhibition hall boasted one of the largest displays of new-to-market, and coming-to-market devices, technologies and other products to make managing diabetes easier, safer and more precise.

But I, and you, are still checking our blood sugar on a glucose meter that's allowed to be anywhere within 20 percent of the laboratory standard 95 percent of the time.

What that means is when my meter says my blood sugar is 145 mg/dl (8 mmol/l) it might be -- or, given the up to plus or minus 20 percent, it might be 113 mg/dl (6.2 mmol/l) or 173 mg/dl (9.6 mmol/l), or anywhere in between.

In 2010 the FDA wrote, "Glucose meters are increasingly being used to achieve tight glycemic control despite the fact that these devices have not been approved for this use." The article goes on to say that patients at home and those in clinical settings are using glucose meters that have not been approved as safe and effective.

Nearly 26 million people have diabetes in the U.S. Nearly 80 million have pre-diabetes. While they don't all use meters, meter accuracy is not limited to a small, exceptional group. Since within 10 years most people with pre-diabetes will go on to get Type 2 diabetes, meter accuracy will grow to affect up to a third of the nation.

So while manufacturers keep adding bells and whistles to meters, and we're on the launch pad for an artificial pancreas -- where accuracy will be even more critical -- why don't I have a meter that gives me an accurate reading of my blood sugar?

Think about it: would you buy a scale that's 20 percent off? Your 145 pounds on the scale might really be 113, 127, 165 or 173 pounds, or anywhere in between. Would you drive a car whose speedometer gave the speed up to plus or minus 20 miles per hour? How useful would a watch be that was sometimes too fast and sometimes too slow and you didn't know when it was which?

Six to 10 times a day when I check my blood sugar, I'm making a decision to either eat more calories -- eating sugar if my blood sugar's too low, to bring it up -- or take more insulin if my blood sugar's too high, to bring it down. And that, my friend, can be a life-threatening action if I'm basing it on faulty numbers.

To minimize some worry, you should know that the governing body, the International Organization for Standardization (ISO), states that the rate of allowable accuracy on your meter must be within 15 percent of the laboratory standard when your blood sugar is lower than 75 mg/dl. But still...

Variance Meter to Meter
Not only do we not know how off the mark our meter readings are, testing your numbers on one meter next to another will drive you mad. Different meters give you different results, almost a different range of results.

Last month at a pre-launch press meeting at Sanofi, I got an iBGStar meter. I've been using Bayer's ContourUSB meter for the last two or three years, so I immediately checked my blood sugar on both meters. For the sake of these lists being difficult to read, here are the results in the U.S. mg/dl value:


I checked twice more over the next day and in each case my ContourUSB showed I was 20-25 points lower than the iBGStar.

Fascinated, I wanted to check on more meters. I had a VerioIQ and Freestyle Lite meter at home and ordered a Freestyle Freedom Lite meter.

Here are my results from eight checks of my blood sugar at the same moment, same finger, using the same drop of blood. (I only checked on Freestyle Freedom Lite twice because it arrived toward the end of my testing.)


Here's another thing that happened when I checked, and then checked again a minute later:


So if you check twice in a row on the same meter you won't necessarily get the same result.

I've been told the only way to know if your meter is accurate is to check your blood sugar on your meter when you're having it drawn for a lab test and compare when the lab test result comes back. I did this two weeks ago. The number on my ContourUSB was 115 mg/dl (6.3 mmol/l). The lab came back with 139 mg/dl (7.7 mmol/l).

While I titled this post "Why Can't Meters Tell Me My Blood Sugar?" I plan to do a second post on "Why Meters Can't Tell Me My Blood Sugar" if that's the case. I want to find out what is at the root of meter readings and disparities and what manufacturers are doing about it.

For now, I've been told the reason for accuracy distortion is largely the interplay between the strip and the meter. Plus a host of other variables like the calibration of the meter, dirt on the meter or strip, what's in your blood from medications you may be taking, what's on your fingers from what you last ate and environmental conditions like climate and altitude.

Here's my plea to the FDA, government, pharma and health insurance companies -- with all the new gizmos and cool designed products, which I applaud, let's also get our priorities straight. When 1 in 20 people with diabetes die from low blood sugar, why are we dragging our feet on getting our meters accurate? What are we waiting for?

So what's your experience? Have you checked on different meters?

Do you think one meter is more accurate than the others? Why?

Have you compared checking your blood sugar on your meter with the hospital standard lab draw?

Have you switched meters and then found you have to get used to new numbers?

On a personal note I want to say to those of us who live with diabetes and constantly feel we are judged by our numbers -- our health care providers judge us, our family may judge us and we judge ourselves -- we really don't know what our numbers are. Plus no matter how hard we work at keeping our blood sugar in our target range, there are other forces at work -- stress, illness, the 20 percent margin of error the FDA allows food manufacturers on food nutrition labels -- that we can't always have the numbers we'd like. Let's try to remember that each time we check our blood sugar and when we do get meter accuracy.

Riva speaks to patients and health care providers about flourishing with diabetes and is the author of "50 Diabetes Myths That Can Ruin Your Life and the 50 Diabetes Truths That Can Save It" and "The ABC's Of Loving Yourself With Diabetes." She is finishing her third book, "Diabetes Dos & How-Tos due out this fall. Visit her website DiabetesStories.com.

For more by Riva Greenberg, click here.

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