Operator Error in Diabetes Testing

by David Mendosa Patient Advocate

Saying that operator error is the biggest problem that people who have diabetes have when we check our blood sugar sounds like blaming the victim. But I'm convinced that some mistakes we make when using our meters and test strips and lancets is the reason why testing so often gives us wacky blood sugar numbers.

People with diabetes know all about blaming the victim. For years I have argued against the common fallacy that diabetes is a lifestyle disease caused by our weight and sloth. In fact, most of us have diabetes in our genes, as the new science of genetic testing shows.

But sometimes -- and not always -- the victim herself or himself causes the error. That's what is going on with some of the inaccurate readings that those of us who have diabetes often get from our blood glucose meters.

For more than 40 years, people who have diabetes have been lucky to be able to check their blood sugar levels at home and when travelling. We can do it whenever we need to do so. We don't have to go to a doctor's office or a hospital or a lab. Consequently, we forgot what a sophisticated testing device we have in our hands. Blood glucose meters are one of very few blood testing devices that the U.S. Food and Drug Administration lets untrained people use.

And we are for the most part completely untrained in how to use our meters. Is it then any wonder that we screw up the procedures once in a while?

Maybe the most common mistake we make is when we don't get enough blood on the test strip. After using dozens of different blood glucose meters since a doctor told me almost 20 years ago that I have diabetes, I know from my own experience that when I don't get quite enough blood on the test strip that the result the meter reports will be off. Usually, it will say that my level is much higher than when I test again right away with a full drop of blood.

Of course, the newer meters require much less blood than then did even just 20 years ago. Some meters can give us accurate results with a blood sample of just 0.3 microliters. That's just a speck of blood, but when we use less than that speck, we still run into inaccurate test results.

We can run into problems even before we get enough blood to satisfy the bloodthirst of our particular meter. I can think of two such problems:

1. Have you ever lanced a finger that you didn't wash just beforehand? If you happen to have some sugar on your finger, the meter could be reporting your dirty finger rather than your clean blood. Since starch turns to glucose in our bodies, I also wonder if having a little flour on our finger might work the same way.

2. Have you ever had to squeeze your finger a whole lot in order to get enough blood? If so, you might be getting interstitial fluid rather than blood. That might give an inaccurate reading. The way to prevent this is not only to wash your hands but to be sure to warm up our hands and the blood in them by using water that is about as hot as you can stand.

Test strip age is another big factor that can skew our blood sugar results. Researchers from the U.S. Centers for Disease Control and Prevention reported in the journal Clinica Chimica Acta how the meters they tested varied a lot. That's something we have no control over and not a question of operator error.

But the CDC researchers also found that the test strips could also be the source of inaccurate readings. They reported that the age of the test strip could also be the source of variability in our blood sugar tests, particularly when we use test strips that are beyond their expiration date. While some meters will reject expired strips, not all of them will. And none of them will reject strips that are nearing their expiration dates, and that too, the CDC researchers told me, can give us inaccurate test results.

My message is for us not to be so quick to blame the companies that sell us the blood sugar meters we rely on to keep our blood sugar levels in check. We are well advised to consider the beam in our own eye before we behold the mote in the eye of our brother.

David Mendosa
Meet Our Writer
David Mendosa

David Mendosa was a journalist who learned in 1994 that he had type 2 diabetes, which he wrote about exclusively. He died in May 2017 after a short illness unrelated to diabetes. He wrote thousands of diabetes articles, two books about it, created one of the first diabetes websites, and published a monthly newsletter, “Diabetes Update.” His very low-carbohydrate diet, A1C level of 5.3, and BMI of 19.8 kept his diabetes in remission without any drugs until his death.