Tricia Fine, manager of customer communications at LifeScan, was kind enough to answer the following letters about meters from our readers.
Seeing the Light
Q: My experience with One Touch II meters has been that they need adequate light. I leave it under a small table light with a 75 watt bulb, and it does fine. If I am in another locations such as on my boat in the twilight hours, I get the “not enough blood” error. I never get this error when it is under a table lamp.
A: Mr. Davis is correct that One Touch meters and all other meters using photometric technology do require adequate light. These meters operate by measuring reflected light under normal environmental lighting conditions. If you attempt to operate the product in extreme lighting conditions such as directly under a very bright light or in very low light conditions, these meters may not operate as designed. While it’s not necessary to test under a table lamp, it’s a good idea to test in lighting conditions that are comfortable for you.
“Not Enough Blood”
Q: I’ve been getting the “not enough }}blood” error about once every twenty tests. One way I’ve found to avoid having to throw a strip away and use a new one (greater costs) is to turn my LifeScan meter off and on, insert “side one” of the calibration strip, remove this strip and insert the regular strip I had used one minute earlier. Results in only five seconds.
This only works if you are reasonably fast. Inserting old dried-up strips just gives an error message. If the sugar levels are above 125 (7.2) you may have to do a regular calibration check afterwards. But at least this is cost free.
A: The “not enough blood” message on One Touch meters is an important safeguard of the system to help ensure accurate results. Under no circumstances should users try to circumvent this warning message. A simple explanation for this occurrence may be that Mr. Floyd occasionally applies a drop of blood that is too small for an accurate test. For proper operation, it is important to apply a large, hanging drop of blood to the target area on the strip. If you ever have reason to believe your LifeScan meter is not operating properly, you should call our customer service department for assistance.
More Meter Talk
Q: In the October issue of Diabetes Health you ran a letter from a fellow, Paul, who had recently purchased a One Touch Profile meter and found that it read much lower than his older Accu-Check II meter. Following this letter there were two replies that chided the author of the first letter for expecting the two meters to be comparable. I think this attitude is absurd. Why shouldn’t they be comparable? They both claim to be measuring the same thing: capillary blood glucose level. If you get a new meter and results are dramatically off from your old meter then one of them is wrong, and you should find out which one it is.
I used to be cowed by meter companies saying that I shouldn’t compare meters. But recently I realized that this didn’t make sense. As a result of the investigations which I will describe, I improved my blood glucose averages significantly.
I have performed numerous simple experiments with the One Touch II meter, with the following results:
- The One Touch II meters give very repeatable readings. If I take a measurement and then immediately take another reading with same meter, 90% of the time the readings are equal or 1 mg/dl apart. The readings are never more than 2 mg/dl apart if I follow the test sequence correctly.
- All of the One Touch II meters read low by a significant amount when compared to laboratory results. Most are low by 20%. The last one I got was low by a whopping 36%.
- I also have an Accu-Check III meter which is usually within five percent of the lab reading. However, its readings are not as repeatable as the One Touch II, and proper technique is very important in getting repeatable readings.
When I got my latest One Touch II and noticed that it was 36% lower than the lab test, I was going to ask LifeScan for a replacement, but my wife had a better idea. She said that the new meter would be just as likely to read low and I should make a conversion chart for converting the One Touch II readings into the more accurate Accu-Check III readings.
I took her suggestion and collected 30 pairs of readings from the meters. Each paired reading was made within one minute. The readings covered the range from 50 mg/dl to 200 mg/dl. I then plotted these readings and found that they were very close to a straight line. Using this plot I made a little correction chart that I taped to the inside cover of my meter. After I converted all readings with this correction scale for a few months, my average BG levels dropped from around 150 to around 117.
According to the recent DCCT study, all such improvements of average BG levels have significant long-lasting positive effects. And I am extremely annoyed that my meter was misleading me into keeping my blood sugar levels 36% higher than they had to be.
It is also a complete mystery to me how the One Touch II meters can produce very repeatable measurements, and yet be so far off from the actual value. With some calibration they could be extremely accurate.
Controlling blood sugar levels is hard work, and an inaccurate meter can basically nullify the payoff of this work. I think it would be helpful for people to know that their meters are not even necessarily 15% accurate and that by calibrating their meters against lab measurements they might get much more reliable readings. Unfortunately, most people don’t have the skills to do such a calibration or to even tell if their meter is capable of being calibrated. Perhaps doctors or meter companies could help out more here. And certainly we shouldn’t chide somebody who notices something is amiss.
A: Mr. Schiller raised some important issues that I would like to clarify for your readers.
First: the difference between meter test results and lab results is not based on capillary blood vs. venous blood as Mr. Schiller suggests. In fact, all blood glucose meters for home use measure whole capillary blood, while lab instruments measure only the serum or plasma portions of the blood, which have had the red blood platelets removed. It is well documented that because of this difference in sample types, whole blood test results are approximately 12% lower than serum plasma test results. Therefore, to accurately compare the two, the laboratory result must be converted into its whole blood equivalent by dividing it by 1.12.
For example, if your lab glucose result is 143 mg/dl you must divide 143 by 1.12 which equals 127 mg/dl. In this example, the 127 mg/dl represents the whole blood equivalent of the lab result, i.e., between 152 and 102. This 15-20% range is designed not only to allow for differences between meters, but also the differences in variations between laboratory systems. If your test results fall outside this range, you should contact the manufacturer for assistance and possible replacement of the product.
Second, at first glance you would think that all meters should provide the same result because they are measuring the same thing, whole blood. However, not all meters are calibrated in the same way. Some products, such as LifeScan’s One Touch meters, are calibrated for whole blood and their results must be converted. Other meters are calibrated somewhere in between whole blood and serum/plasma, and still others are already calibrated for serum/plasma equivalents. This is why manufacturers tell consumers that the only way to check the accuracy of a meter is to compare its test results to a lab result, and not another meter.
Third, while Mr. Schiller’s method of comparing 30 sets of blood glucose values from his two different meters and making his own conversion chart is enterprising, this method should not be used as a substitute for using a lab test to confirm the accuracy of a meter. There are a number of factors that may have influenced Mr. Schiller’s results. For example, were the blood samples taken from separate finger sticks? If not, cellular fluid released by cells damaged by the finger stick will begin to dilute the blood if more than one sample is taken from the same and taken without any time delay? If not, readings will vary, even among two meters of the same brand. Were both meters clean and kept clean throughout the tests? Any lint, dirt, or blood blocking the test strip holder or optic window can affect results. Were the test strips fresh and had they been stored properly with the vial lid closed securely? Test strips exposed to heat and moisture extremes outside their recommended limits will yield potentially different results. In clinical tests to determine accuracy, there are rigid protocols that are followed to insure that these and many other variables are controlled. It would be very difficult for the average consumer to duplicate such conditions.
At LifeScan we applaud Mr. Schiller’s dedication to controlling his diabetes. Frequent blood glucose monitoring is an important tool that can help people with diabetes and their doctors understand the effects of medication, diet, and exercise on their blood glucose levels. However, treatment decisions based on blood glucose test results should always be made with the knowledge and approval of your doctor. If you suspect your meter is not operating properly, please contact the manufacturer. We’re here to help 24 hours a day, seven days a week.